Latency reduction in LTE systems

ABSTRACT

Systems, methods, and instrumentalities are disclosed for a wireless transmit/receive unit (WTRU) autonomously synchronizing. For example, a WTRU may be configured to receive a downlink timing synchronization. The WTRU may be configured to determine a synchronization signal. The WTRU may be configured to determine a synchronization mode. The synchronization mode may be RRC CONNECTED mode. The synchronization mode may be RRC IDLE mode. The WTRU may communicate data to the network while in an unsynchronized state in an RRC IDLE and/or an RRC CONNECTED mode. The communication of data while unsynchronized may reduce latency relative to one or more of a random access channel (RACH) procedure, a resource radio control (RRC) connection establishment procedure, or a data packet scheduling, for example.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage entry under 35 U.S.C. § 371 ofPatent Cooperation Treaty Application PCT/US2015/000474, filed Dec. 23,2015, which claims the benefit of U.S. Provisional Patent ApplicationNo. 62/096,221, filed on Dec. 23, 2014, and U.S. Provisional PatentApplication No. 62/219,981, filed on Sep. 17, 2015, the contents of allof which being hereby incorporated by reference as if fully set-forthherein in their respective entirety, for all purposes.

BACKGROUND

Transmission latency for data in the eNB for downlink transmissions orin the WTRU for uplink transmissions may be reduced.

SUMMARY

Systems, methods, and instrumentalities are disclosed for a wirelesstransmit/receive unit (WTRU) autonomously synchronizing. For example, aWTRU may be configured to receive a downlink timing synchronization. TheWTRU may be configured to determine a synchronization signal. The WTRUmay be configured to determine a synchronization mode. Thesynchronization mode may be RRC CONNECTED mode. The synchronization modemay be RRC IDLE mode.

A WTRU may be configured to determine to transmit an uplink transmissionrequest. The WTRU may be configured to determine the number oftransmissions of the uplink transmission request. The WTRU may beconfigured to determine the success of the uplink transmission request,for example, based on the number of transmissions of the uplinktransmission request.

One or more techniques for communicating data may be performed by awireless transmit/receive unit (WTRU). Techniques may includedetermining, by the WTRU, that at least one of: control plane data oruser plane data is available for transmission to a network. Techniquesmay include determining, by the WTRU, that the WTRU is in at least oneof: a radio resource control (RRC) IDLE mode or a RRC CONNECTED mode.Techniques may include determining, by the WTRU, that the WTRU is in anunsynchronized state relative to the network. Techniques may includesending a transmission from the WTRU in the unsynchronized state, via aphysical uplink channel to the network. The transmission may include theat least one of the control plane data or the user plane data and/or anuplink timing synchronization request. Techniques may include receiving,by the WTRU, at least one of a timing advance command (TAC) or atransmit power command (TPC) from the network in response to thetransmission.

An evolved NodeB (eNB) may comprise a receiver that may be configured atleast to receive a transmission from a wireless transmit/receive unit(WTRU) in an unsynchronized state relative to the eNB, via a physicaluplink channel. The WTRU may be in at least one of: a radio resourcecontrol (RRC) IDLE mode or a RRC CONNECTED mode. The transmission mayinclude at least one of control plane data or the user plane data and/oran uplink timing synchronization request. The eNB may include aprocessor that may be configured at least to identify the at least oneof control plane data or the user plane data. The processor may beconfigured to identify the uplink timing synchronization request. Theprocessor may be configured to determine at least one of a timingadvance command (TAC) or a transmit power command (TPC) for the WTRU.The eNB may include a transmitter that may be configured at least tosend the at least one of the TAC or TPC to the WTRU in response to thetransmission.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawings.

FIG. 1A is a system diagram of an example communications system in whichone or more disclosed embodiments may be implemented.

FIG. 1B is a system diagram of an example wireless transmit/receive unit(WTRU) that may be used within the communications system illustrated inFIG. 1A.

FIG. 1C is a system diagram of an example radio access network and anexample core network that may be used within the communications systemillustrated in FIG. 1A.

FIG. 1D is a system diagram of an example radio access network and anexample core network that may be used within the communications systemillustrated in FIG. 1A.

FIG. 1E is a system diagram of an example radio access network and anexample core network that may be used within the communications systemillustrated in FIG. 1A.

FIG. 2 illustrates example transmission bandwidths for a wirelesstransmit/receive unit (WTRU).

FIG. 3 illustrates an example of spectrum allocation.

FIG. 4 illustrates an example of frame structure and timingrelationships for TDD duplexing.

FIG. 5 illustrates an example of frame structure and timingrelationships for FDD duplexing.

FIG. 6 is an example of signaling for RSSC, DSS, L3 ConnectionReactivation, extended paging, and eSR.

FIG. 7 is an example of signaling for NW-initiated L3 Reactivation inRRC Idle state.

FIG. 8 is an example of signaling for WTRU-initiated L3 Reactivation inRRC Idle state.

FIG. 9 is an example of signaling for Downlink Data Arrival in RRCConnected state.

FIG. 10 is an example of signaling for Uplink Data Arrival in RRCConnected state.

DETAILED DESCRIPTION

A detailed description of illustrative embodiments will now be describedwith reference to the various Figures. Although this descriptionprovides a detailed example of possible implementations, it should benoted that the details are intended to be examples and in no way limitthe scope of the application. As used herein, the articles “a” and “an”,absent further qualification or characterization, may be understood tomean “one or more” or “at least one”, for example.

FIG. 1A is a diagram of an example communications system 100 in whichone or more disclosed embodiments may be implemented. The communicationssystem 100 may be a multiple access system that provides content, forexample voice, data, video, messaging, broadcast, etc., to multiplewireless users. The communications system 100 may enable multiplewireless users to access such content through the sharing of systemresources, including wireless bandwidth. For example, the communicationssystems 100 may employ one or more channel access methods, for examplecode division multiple access (CDMA), time division multiple access(TDMA), frequency division multiple access (FDMA), orthogonal FDMA(OFDMA), single-carrier FDMA (SC-FDMA), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, and/or 102 d (whichgenerally or collectively may be referred to as WTRU 102), a radioaccess network (RAN) 103/104/105, a core network 106/107/109, a publicswitched telephone network (PSTN) 108, the Internet 110, and othernetworks 112, though it will be appreciated that the disclosedembodiments contemplate any number of WTRUs, base stations, networks,and/or network elements. Each of the WTRUs 102 a, 102 b, 102 c, 102 dmay be any type of device configured to operate and/or communicate in awireless environment. By way of example, the WTRUs 102 a, 102 b, 102 c,102 d may be configured to transmit and/or receive wireless signals andmay include a user equipment (WTRU), a mobile station, a fixed or mobilesubscriber unit, a pager, a cellular telephone, a personal digitalassistant (PDA), a smartphone, a laptop, a netbook, a personal computer,a wireless sensor, consumer electronics, and the like.

The communications systems 100 may also include a base station 114 a anda base station 114 b. Each of the base stations 114 a, 114 b may be anytype of device configured to wirelessly interface with at least one ofthe WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to one or morecommunication networks, for example the core network 106/107/109, theInternet 110, and/or the networks 112. By way of example, the basestations 114 a, 114 b may be a base transceiver station (BTS), a Node-B,an eNode B, a Home Node B, a Home eNode B, a site controller, an accesspoint (AP), a wireless router, and the like. While the base stations 114a, 114 b are each depicted as a single element, it will be appreciatedthat the base stations 114 a, 114 b may include any number ofinterconnected base stations and/or network elements.

The base station 114 a may be part of the RAN 103/104/105, which mayalso include other base stations and/or network elements (not shown),for example a base station controller (BSC), a radio network controller(RNC), relay nodes, etc. The base station 114 a and/or the base station114 b may be configured to transmit and/or receive wireless signalswithin a particular geographic region, which may be referred to as acell (not shown). The cell may further be divided into cell sectors. Forexample, the cell associated with the base station 114 a may be dividedinto three sectors. Thus, in one embodiment, the base station 114 a mayinclude three transceivers, i.e., one for each sector of the cell. In anembodiment, the base station 114 a may employ multiple-input multipleoutput (MIMO) technology and, therefore, may utilize multipletransceivers for each sector of the cell.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 115/116/117,which may be any suitable wireless communication link (e.g., radiofrequency (RF), microwave, infrared (IR), ultraviolet (UV), visiblelight, etc.). The air interface 115/116/117 may be established using anysuitable radio access technology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, for example CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 103/104/105 and the WTRUs 102a, 102 b, 102 c may implement a radio technology such as UniversalMobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA),which may establish the air interface 115/116/117 using wideband CDMA(WCDMA). WCDMA may include communication protocols such as High-SpeedPacket Access (HSPA) and/or Evolved HSPA (HSPA+). HSPA may includeHigh-Speed Downlink Packet Access (HSDPA) and/or High-Speed UplinkPacket Access (HSUPA).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement a radio technology such as Evolved UMTS TerrestrialRadio Access (E-UTRA), which may establish the air interface 115/116/117using Long Term Evolution (LTE) and/or LTE-Advanced (LTE-A).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement radio technologies such as IEEE 802.16 (i.e., WorldwideInteroperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1×,CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95(IS-95), Interim Standard 856 (IS-856), Global System for Mobilecommunications (GSM), Enhanced Data rates for GSM Evolution (EDGE), GSMEDGE (GERAN), and the like.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, forexample a place of business, a home, a vehicle, a campus, and the like.In one embodiment, the base station 114 b and the WTRUs 102 c, 102 d mayimplement a radio technology such as IEEE 802.11 to establish a wirelesslocal area network (WLAN). In an embodiment, the base station 114 b andthe WTRUs 102 c, 102 d may implement a radio technology such as IEEE802.15 to establish a wireless personal area network (WPAN). In yet anembodiment, the base station 114 b and the WTRUs 102 c, 102 d mayutilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A,etc.) to establish a picocell or femtocell. As shown in FIG. 1A, thebase station 114 b may have a direct connection to the Internet 110.Thus, the base station 114 b may not be required to access the Internet110 via the core network 106/107/109.

The RAN 103/104/105 may be in communication with the core network106/107/109, which may be any type of network configured to providevoice, data, applications, and/or voice over internet protocol (VoIP)services to one or more of the WTRUs 102 a, 102 b, 102 c, 102 d. Forexample, the core network 106/107/109 may provide call control, billingservices, mobile location-based services, pre-paid calling, Internetconnectivity, video distribution, etc., and/or perform high-levelsecurity functions, for example user authentication. Although not shownin FIG. 1A, it will be appreciated that the RAN 103/104/105 and/or thecore network 106/107/109 may be in direct or indirect communication withother RANs that employ the same RAT as the RAN 103/104/105 or adifferent RAT. For example, in addition to being connected to the RAN103/104/105, which may be utilizing an E-UTRA radio technology, the corenetwork 106/107/109 may also be in communication with a RAN (not shown)employing a GSM radio technology.

The core network 106/107/109 may also serve as a gateway for the WTRUs102 a, 102 b, 102 c, 102 d to access the PSTN 108, the Internet 110,and/or other networks 112. The PSTN 108 may include circuit-switchedtelephone networks that provide plain old telephone service (POTS). TheInternet 110 may include a global system of interconnected computernetworks and devices that use common communication protocols, forexample the transmission control protocol (TCP), user datagram protocol(UDP) and the internet protocol (IP) in the TCP/IP internet protocolsuite. The networks 112 may include wired or wireless communicationsnetworks owned and/or operated by other service providers. For example,the networks 112 may include a core network connected to one or moreRANs, which may employ the same RAT as the RAN 103/104/105 or adifferent RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities, i.e., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks. For example, the WTRU 102 c shown in FIG. 1A may be configured tocommunicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram of an example WTRU 102. As shown in FIG. 1B,the WTRU 102 may include a processor 118, a transceiver 120, atransmit/receive element 122, a speaker/microphone 124, a keypad 126, adisplay/touchpad 128, non-removable memory 130, removable memory 132, apower source 134, a global positioning system (GPS) chipset 136, andother peripherals 138. It will be appreciated that the WTRU 102 mayinclude any sub-combination of the foregoing elements while remainingconsistent with an embodiment. Also, embodiments contemplate that thebase stations 114 a and 114 b, and/or the nodes that base stations 114 aand 114 b may represent, for example but not limited to transceiverstation (BTS), a Node-B, a site controller, an access point (AP), a homenode-B, an evolved home node-B (eNodeB), a home evolved node-B (HeNB), ahome evolved node-B gateway, and proxy nodes, among others, may includesome or each of the elements depicted in FIG. 1B and described herein.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Array (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 115/116/117. For example, in one embodiment,the transmit/receive element 122 may be an antenna configured totransmit and/or receive RF signals. In an embodiment, thetransmit/receive element 122 may be an emitter/detector configured totransmit and/or receive IR, UV, or visible light signals, for example.In yet an embodiment, the transmit/receive element 122 may be configuredto transmit and receive both RF and light signals. It will beappreciated that the transmit/receive element 122 may be configured totransmit and/or receive any combination of wireless signals.

In addition, although the transmit/receive element 122 is depicted inFIG. 1B as a single element, the WTRU 102 may include any number oftransmit/receive elements 122. More specifically, the WTRU 102 mayemploy MIMO technology. Thus, in one embodiment, the WTRU 102 mayinclude two or more transmit/receive elements 122 (e.g., multipleantennas) for transmitting and receiving wireless signals over the airinterface 115/116/117.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, for example UTRA and IEEE 802.11,for example.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,for example the non-removable memory 130 and/or the removable memory132. The non-removable memory 130 may include random-access memory(RAM), read-only memory (ROM), a hard disk, or any other type of memorystorage device. The removable memory 132 may include a subscriberidentity module (SIM) card, a memory stick, a secure digital (SD) memorycard, and the like. In an embodiment, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, for example on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 115/116/117from a base station (e.g., base stations 114 a, 114 b) and/or determineits location based on the timing of the signals being received from twoor more nearby base stations. It will be appreciated that the WTRU 102may acquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, and the like.

FIG. 1C is a system diagram of the RAN 103 and the core network 106according to an embodiment. As noted above, the RAN 103 may employ aUTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102 cover the air interface 115. The RAN 103 may also be in communicationwith the core network 106. As shown in FIG. 1C, the RAN 103 may includeNode-Bs 140 a, 140 b, 140 c, which may each include one or moretransceivers for communicating with the WTRUs 102 a, 102 b, 102 c overthe air interface 115. The Node-Bs 140 a, 140 b, 140 c may each beassociated with a particular cell (not shown) within the RAN 103. TheRAN 103 may also include RNCs 142 a, 142 b. It will be appreciated thatthe RAN 103 may include any number of Node-Bs and RNCs while remainingconsistent with an embodiment.

As shown in FIG. 1C, the Node-Bs 140 a, 140 b may be in communicationwith the RNC 142 a. Additionally, the Node-B 140 c may be incommunication with the RNC 142 b. The Node-Bs 140 a, 140 b, 140 c maycommunicate with the respective RNCs 142 a, 142 b via an Iub interface.The RNCs 142 a, 142 b may be in communication with one another via anIur interface. Each of the RNCs 142 a, 142 b may be configured tocontrol the respective Node-Bs 140 a, 140 b, 140 c to which it isconnected. In addition, each of the RNCs 142 a, 142 b may be configuredto carry out or support other functionality, for example outer looppower control, load control, admission control, packet scheduling,handover control, macro diversity, security functions, data encryption,and the like.

The core network 106 shown in FIG. 1C may include a media gateway (MGW)144, a mobile switching center (MSC) 146, a serving GPRS support node(SGSN) 148, and/or a gateway GPRS support node (GGSN) 150. While each ofthe foregoing elements are depicted as part of the core network 106, itwill be appreciated that any one of these elements may be owned and/oroperated by an entity other than the core network operator.

The RNC 142 a in the RAN 103 may be connected to the MSC 146 in the corenetwork 106 via an IuCS interface. The MSC 146 may be connected to theMGW 144. The MSC 146 and the MGW 144 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, for example the PSTN108, to facilitate communications between the WTRUs 102 a, 102 b, 102 cand traditional land-line communications devices.

The RNC 142 a in the RAN 103 may also be connected to the SGSN 148 inthe core network 106 via an IuPS interface. The SGSN 148 may beconnected to the GGSN 150. The SGSN 148 and the GGSN 150 may provide theWTRUs 102 a, 102 b, 102 c with access to packet-switched networks, forexample the Internet 110, to facilitate communications between and theWTRUs 102 a, 102 b, 102 c and IP-enabled devices.

As noted above, the core network 106 may also be connected to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

FIG. 1D is a system diagram of the RAN 104 and the core network 107according to an embodiment. As noted above, the RAN 104 may employ anE-UTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102c over the air interface 116. The RAN 104 may also be in communicationwith the core network 107.

The RAN 104 may include eNode-Bs 160 a, 160 b, 160 c, though it will beappreciated that the RAN 104 may include any number of eNode-Bs whileremaining consistent with an embodiment. The eNode-Bs 160 a, 160 b, 160c may each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the eNode-Bs 160 a, 160 b, 160 c may implement MIMO technology. Thus,the eNode-B 160 a, for example, may use multiple antennas to transmitwireless signals to, and receive wireless signals from, the WTRU 102 a.

Each of the eNode-Bs 160 a, 160 b, 160 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the uplink and/or downlink, and the like. As shown in FIG. 1D, theeNode-Bs 160 a, 160 b, 160 c may communicate with one another over an X2interface.

The core network 107 shown in FIG. 1D may include a mobility managementgateway (MME) 162, a serving gateway 164, and a packet data network(PDN) gateway 166. While each of the foregoing elements are depicted aspart of the core network 107, it will be appreciated that any one ofthese elements may be owned and/or operated by an entity other than thecore network operator.

The MME 162 may be connected to each of the eNode-Bs 160 a, 160 b, 160 cin the RAN 104 via an S1 interface and may serve as a control node. Forexample, the MME 162 may be responsible for authenticating users of theWTRUs 102 a, 102 b, 102 c, bearer activation/deactivation, selecting aparticular serving gateway during an initial attach of the WTRUs 102 a,102 b, 102 c, and the like. The MME 162 may also provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, for example GSM or WCDMA.

The serving gateway 164 may be connected to each of the eNode-Bs 160 a,160 b, 160 c in the RAN 104 via the S1 interface. The serving gateway164 may generally route and forward user data packets to/from the WTRUs102 a, 102 b, 102 c. The serving gateway 164 may also perform otherfunctions, for example anchoring user planes during inter-eNode Bhandovers, triggering paging when downlink data is available for theWTRUs 102 a, 102 b, 102 c, managing and storing contexts of the WTRUs102 a, 102 b, 102 c, and the like.

The serving gateway 164 may also be connected to the PDN gateway 166,which may provide the WTRUs 102 a, 102 b, 102 c with access topacket-switched networks, for example the Internet 110, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and IP-enableddevices.

The core network 107 may facilitate communications with other networks.For example, the core network 107 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, for example the PSTN108, to facilitate communications between the WTRUs 102 a, 102 b, 102 cand traditional land-line communications devices. For example, the corenetwork 107 may include, or may communicate with, an IP gateway (e.g.,an IP multimedia subsystem (IMS) server) that serves as an interfacebetween the core network 107 and the PSTN 108. In addition, the corenetwork 107 may provide the WTRUs 102 a, 102 b, 102 c with access to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

FIG. 1E is a system diagram of the RAN 105 and the core network 109according to an embodiment. The RAN 105 may be an access service network(ASN) that employs IEEE 802.16 radio technology to communicate with theWTRUs 102 a, 102 b, 102 c over the air interface 117. As will be furtherdiscussed below, the communication links between the differentfunctional entities of the WTRUs 102 a, 102 b, 102 c, the RAN 105, andthe core network 109 may be defined as reference points.

As shown in FIG. 1E, the RAN 105 may include base stations 180 a, 180 b,180 c, and an ASN gateway 182, though it will be appreciated that theRAN 105 may include any number of base stations and ASN gateways whileremaining consistent with an embodiment. The base stations 180 a, 180 b,180 c may each be associated with a particular cell (not shown) in theRAN 105 and may each include one or more transceivers for communicatingwith the WTRUs 102 a, 102 b, 102 c over the air interface 117. In oneembodiment, the base stations 180 a, 180 b, 180 c may implement MIMOtechnology. Thus, the base station 180 a, for example, may use multipleantennas to transmit wireless signals to, and receive wireless signalsfrom, the WTRU 102 a. The base stations 180 a, 180 b, 180 c may alsoprovide mobility management functions, for example handoff triggering,tunnel establishment, radio resource management, traffic classification,quality of service (QoS) policy enforcement, and the like. The ASNgateway 182 may serve as a traffic aggregation point and may beresponsible for paging, caching of subscriber profiles, routing to thecore network 109, and the like.

The air interface 117 between the WTRUs 102 a, 102 b, 102 c and the RAN105 may be defined as an R1 reference point that implements the IEEE802.16 specification. In addition, each of the WTRUs 102 a, 102 b, 102 cmay establish a logical interface (not shown) with the core network 109.The logical interface between the WTRUs 102 a, 102 b, 102 c and the corenetwork 109 may be defined as an R2 reference point, which may be usedfor authentication, authorization, IP host configuration management,and/or mobility management.

The communication link between each of the base stations 180 a, 180 b,180 c may be defined as an R8 reference point that includes protocolsfor facilitating WTRU handovers and the transfer of data between basestations. The communication link between the base stations 180 a, 180 b,180 c and the ASN gateway 182 may be defined as an R6 reference point.The R6 reference point may include protocols for facilitating mobilitymanagement based on mobility events associated with each of the WTRUs102 a, 102 b, 102 c.

As shown in FIG. 1E, the RAN 105 may be connected to the core network109. The communication link between the RAN 105 and the core network 109may defined as an R3 reference point that includes protocols forfacilitating data transfer and mobility management capabilities, forexample. The core network 109 may include a mobile IP home agent(MIP-HA) 184, an authentication, authorization, accounting (AAA) server186, and a gateway 188. While each of the foregoing elements aredepicted as part of the core network 109, it will be appreciated thatany one of these elements may be owned and/or operated by an entityother than the core network operator.

The MIP-HA may be responsible for IP address management, and may enablethe WTRUs 102 a, 102 b, 102 c to roam between different ASNs and/ordifferent core networks. The MIP-HA 184 may provide the WTRUs 102 a, 102b, 102 c with access to packet-switched networks, for example theInternet 110, to facilitate communications between the WTRUs 102 a, 102b, 102 c and IP-enabled devices. The AAA server 186 may be responsiblefor user authentication and for supporting user services. The gateway188 may facilitate interworking with other networks. For example, thegateway 188 may provide the WTRUs 102 a, 102 b, 102 c with access tocircuit-switched networks, for example the PSTN 108, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and traditionalland-line communications devices. In addition, the gateway 188 mayprovide the WTRUs 102 a, 102 b, 102 c with access to the networks 112,which may include other wired or wireless networks that are owned and/oroperated by other service providers.

Although not shown in FIG. 1E, it will be appreciated that the RAN 105may be connected to other ASNs and the core network 109 may be connectedto other core networks. The communication link between the RAN 105 theother ASNs may be defined as an R4 reference point, which may includeprotocols for coordinating the mobility of the WTRUs 102 a, 102 b, 102 cbetween the RAN 105 and the other ASNs. The communication link betweenthe core network 109 and the other core networks may be defined as an R5reference, which may include protocols for facilitating interworkingbetween home core networks and visited core networks.

For purposes of illustration and explanation, and not limitation, one ormore of the examples described herein may refer to one or more of thefollowing acronyms:

-   Δf Sub-carrier spacing-   5gFlex 5G Flexible Radio Access Technology-   5gNB 5GFlex NodeB-   ACK Acknowledgement-   BLER Block Error Rate-   BTI Basic TI (in integer multiple of one or more symbol duration)-   CB Contention-Based (e.g. access, channel, resource)-   CoMP Coordinated Multi-Point transmission/reception-   CP Cyclic Prefix-   CP-OFDM Conventional OFDM (relying on cyclic prefix)-   CQI Channel Quality Indicator-   CN Core Network (e.g. LTE packet core)-   CRC Cyclic Redundancy Check-   CSI Channel State Information-   D2D Device to Device transmissions (e.g. LTE Sidelink)-   DCI Downlink Control Information-   DL Downlink-   DM-RS Demodulation Reference Signal-   DRB Data Radio Bearer-   EPC Evolved Packet Core-   FBMC Filtered Band Multi-Carrier-   FBMC/OQAM A FBMC technique using Offset Quadrature Amplitude    Modulation-   FDD Frequency Division Duplexing-   FDM Frequency Division Multiplexing-   ICC Industrial Control and Communications-   ICIC Inter-Cell Interference Cancellation-   IP Internet Protocol-   LAA License Assisted Access-   LBT Listen-Before-Talk-   LCI-1 Logical Channel-   LCP Logical Channel Prioritization-   LTE Long Term Evolution e.g. from 3GPP LIE R8 and up-   MAC Medium Access Control-   NACK Negative ACK-   MC MultiCarrier-   MCS Modulation and Coding Scheme-   MIMO Multiple Input Multiple Output-   MTC Machine-Type Communications-   NAS Non-Access Stratum-   OFDM Orthogonal Frequency-Division Multiplexing-   OOB Out-Of-Band (emissions)-   OQAM Offset Quadrature Amplitude Modulation-   P_(cmax) Total available UE/WTRU power in a given TI-   PHY Physical Layer-   PRACH Physical Random Access Channel-   PDU Protocol Data Unit-   PER Packet Error Rate-   PLR Packet Loss Rate-   QoS Quality of Service (from the physical layer perspective)-   RAB Radio Access Bearer-   RACH Random Access Channel (or procedure)-   RF Radio Front end-   RNTI Radio Network Identifier-   RRC Radio Resource Control-   RRM Radio Resource Management-   RS Reference Signal-   RTT Round-Trip Time-   SCMA Single Carrier Multiple Access-   SDU Service Data Unit-   SOM Spectrum Operation Mode-   SS Synchronization Signal-   SRB Signalling Radio Bearer-   SWG Switching Gap (in a self-contained subframe)-   TB Transport Block-   TDD Time-Division Duplexing-   TDM Time-Division Multiplexing-   TI Time Interval (in integer multiple of one or more BTI)-   TTI Transmission Time Interval (in integer multiple of one or more    TI)-   TRx Transceiver-   UFMC Universal Filtered MultiCarrier-   UF-OFDM Universal Filtered OFDM-   UL Uplink-   V2V Vehicle to vehicle communications-   V2X Vehicular communications-   WLAN Wireless Local Area Networks and related technologies (IEEE    802.xx domain)

LTE R8/9 Single Cell Operation is contemplated. 3GPP LTE Release 8/9(LTE R8/9) may support up to 100 Mbps in the downlink (DL), and 50 Mbpsin the uplink (UL) for a 2×2 configuration. The LTE downlinktransmission scheme may be based on an Orthogonal Frequency-DivisionMultiple Access (OFDMA) air interface.

For flexible deployment, LTE R8/9/10 systems may support scalabletransmission bandwidths, which may be one of [1.4, 2.5, 5, 10, 15 or 20]MHz.

In LTE R8/9 (e.g., or LTE R10), one or more (e.g., each) radio frame (10ms) may consist of 10 sub-frames of 1 ms. One or more (e.g., each)sub-frame may consist of one or more (e.g., two) timeslots of 0.5 mseach. There may be seven or six OFDM symbols per timeslot. Seven symbolsper timeslot may be used with normal cyclic prefix length, and sixsymbols per timeslot may be used with the extended cyclic prefix length.The sub-carrier spacing for the LTE R8/9 system may be 15 kHz. A reducedsub-carrier spacing mode using 7.5 kHz may be utilized.

A resource element (RE) may correspond to one or more sub-carriersduring one or more OFDM symbol intervals. Twelve sub-carriers (e.g.,consecutive sub-carriers) during a 0.5 ms timeslot may constitute oneresource block (RB). With seven symbols per timeslot, each RB mayconsists of 12*7=84 REs. A DL carrier may consist of 6 RBs to 110 RBs,for example, corresponding to an overall scalable transmission bandwidthof roughly 1 MHz to 20 MHz. Each transmission bandwidth, e.g. 1.4, 3, 5,10 or 20 MHz, may correspond to a number of RBs.

The basic time-domain unit for dynamic scheduling may be one sub-frameconsisting of two consecutive timeslots. This may be referred to as aresource-block pair. Certain sub-carriers on some OFDM symbols may beallocated to carry pilot signals in the time-frequency grid. A number ofsub-carriers at the edges of the transmission bandwidth might not betransmitted, for example, in order to comply with spectral maskrequirements.

In LTE R8/9 and for R10 in single carrier configuration where thenetwork may assign the WTRU one pair of UL and DL carriers (e.g., FDD)or one carrier time shared for UL and DL (e.g., TDD), for a givensubframe there may be a single Hybrid Automatic Repeat request (HARQ)process active for the UL and a single HARQ process active in the DL.

Maintenance of Uplink Timing for LTE is contemplated. In legacy LTEsystems, the WTRU may apply a timing advance (e.g., using N_(TA), forframe structure 1) to one or more of SRS, PUCCH and/or PUSCHtransmission. For example, the WTRU may perform the uplink transmissionby applying a time offset N_(TA)×Ts from the start of the correspondingdownlink subframe. The WTRU may use the DL Timing Reference for one ormore purposes. For example, the WTRU may use a DL timing reference todetect DL frame/subframe boundaries (e.g., based on CRS/PSS/SSS), forframe/subframe processing (e.g., timing lock). A WTRU may use a DLtiming reference to determine a timing advance reference (N_(TA) _(_)_(REF)) using one or more techniques (e.g., as described in 3GPPTS36.133). When performing preamble transmission (e.g., during a randomaccess procedure), the WTRU may use N_(TA) _(_) _(REF)=N_(TA)=0. Thetiming reference (N_(TA) _(_) _(REF)) may be updated upon reception of aRAR TAC, and N_(TA) may also be set to N_(TA) _(_) _(REF). The timingreference (N_(TA) _(_) _(REF)) may be updated upon reception of a MACTAC CE, and N_(TA) may be reset to the updated value of N_(TA) _(_)_(REF). The DL timing reference may be used to determine the amount ofWTRU-autonomous timing adjustment to apply to SRS, PUCCH and PUSCHtransmissions (as adjustment to the value of N_(TA) as defined by 3GPPTS36.213), in a frame for which the WTRU performs an uplink transmissionand for which the WTRU does not apply a TAC. For example, whenperforming a transmission (e.g., the transmission after a DRX period),the WTRU may set its uplink timing (N_(TA)) such that the UL timingerror with respect to the DL timing is, e.g., within +/−T_(e). Forexample, when performing a transmission (e.g., subsequent transmissionsafter a DRX period, and/or if the WTRU was not in DRX), the WTRU mayautonomously adjust its timing (N_(TA)) if the difference between theWTRU's timing and/or the timing of the frame used for applying thetiming advance for the uplink transmission exceeds a certain valueT_(e).

The WTRU may perform the autonomous adjustments, described herein, forN_(TA), but may, for example, ensure the adjustment amount is bounded byone or more of a maximum adjustment action, minimum adjustment rate,and/or maximum adjustment rate (e.g., as described in 3GPP TS36.133).The WTRU-autonomous timing evaluation may be performed dynamically(e.g., in the range of a few subframes) when the WTRU is synchronizedand/or in DRX Active Time (if configured). Network-controlledadjustments using TAC may be somewhat slower and typically received atintervals corresponding to half the value of the configured TAT (e.g.,500 ms, 750 ms, . . . 10240 ms, infinity).

LTE R10/11 CA_Multiple Cell Operation and/or Intra-eNB CarrierAggregation is contemplated. LTE-Advanced with Carrier Aggregation (LTECA R10) may be an evolution to improve single carrier LTE data ratesusing, for example, bandwidth extensions. Bandwidth extensions may bereferred to as Carrier Aggregation (CA). With CA, the WTRU may transmitand receive simultaneously over the Physical Uplink Shared Channel(PUSCH) and the Physical Downlink Shared Channel (PDSCH) of multipleserving cells. One or more (e.g., up to four) secondary serving cells(SCells) may be used in addition to a Primary serving Cell (PCell) andmay support flexible bandwidth assignments up to 100 MHz. Uplink ControlInformation (UCI) may consist of HARQ ACK/NACK feedback and/or ChannelState Information (CSI). UCI may be transmitted either on PhysicalUplink Control Channel (PUCCH) resources of the PCell or on PUSCHresources available for a serving cell configured for uplinktransmissions.

The control information for the scheduling of PDSCH and PUSCH may besent on one or more Physical Data Control Channel(s) (PDCCH). Inaddition to the LTE R8/9 scheduling using one PDCCH for a pair of UL andDL carriers, cross-carrier scheduling may be supported by a given PDCCH,for example, allowing the network to provide PDSCH assignments and/orPUSCH grants for transmissions in other serving cell(s).

There may be one HARQ entity for one or more (e.g., each) serving cell,where one or more (e.g., each) entity may have up to 8 HARQ processes(e.g., one per subframe for one round-trip time (RTT)), for example, fora FDD LTE R10 UE/WTRU operating with CA. There may be more than one HARQprocess active for the UL and for the DL in any given subframe. Theremay be a UL (e.g., at most one UL) and a DL HARQ process per configuredserving cell.

Scheduling principles is contemplated. In LTE R8/9/10+, the PDCCH may beused by the network (e.g., NW or eNB) to assign resources for downlinktransmissions on the PDSCH and/or to grant resources for uplinktransmissions on the PUSCH to the terminal device (e.g., WTRU).

A WTRU may request radio resources for an uplink transmission, forexample, by sending a scheduling request (SR) to the eNB. The SR may betransmitted on dedicated resources (D-SR) on the Physical Uplink ControlChannel (PUCCH) if configured. The SR may be transmitted using theRandom Access procedure (RACH) (e.g., RA-SR).

The eNB may grant radio resources to the WTRU for a transmission onPUSCH, for example, indicated in a grant received on the PDCCH inconfigured resources (e.g., a Semi-Persistently Scheduled UL grant).

The WTRU may include, for example, in an uplink transmission, a BufferStatus Report (BSR), indicating the amount of data in the WTRU's buffer.The trigger to transmit a BSR may trigger a scheduling request.

Control signalling for scheduling and PDCCH monitoring may be disclosedherein. The WTRU may determine whether or not it needs to act on controlsignalling in a given sub-frame, for example, by monitoring the PDCCHfor specific data control information messages (DCI formats). DCIformats may be masked using a known radio network temporary identifier(RNTI) in specific locations, or search space, using differentcombinations of physical resources (e.g., control channel elements(CCEs)) based on aggregation levels (AL) (e.g., each corresponding toeither 1, 2, 4, or 8 CCEs). A CCE may consist of 36 QPSK symbols, or 72channel coded bits.

Scheduling control information in an uplink grant may include a New DataIndicator (NDI). An NDI may be used to determine whether the grant isfor an initial transmission or for a retransmission. A resourceassignment that may indicate what physical resources blocks (PRBs) intime and frequency may be allocated to the transmission and a Modulationand Coding Scheme (MCS). A WTRU may determine the size of the associatedtransport block (TB) from the MCS and the number of PRBs allocated tothe transmission.

LTE R12+Dual Connectivity, Multiple Cell Operation, and/or Inter-eNB CAis contemplated. In LTE R12 (e.g., or later, for aspects of multi-celloperation using inter-eNB carrier aggregation), the WTRU may beconfigured with some form dual connectivity, such as a configuration inwhich the WTRU may have access to resources of cells associated todifferent eNBs. The network may control connectivity using a singleMME/S1-c connection terminating in the MeNB.

Control plane aspects are contemplated. From the perspective of thecontrol plane, the WTRU may have established a RRC connection with afirst eNB (e.g., a MeNB) and may support a configuration where one ormore cells may be associated to a second eNB (e.g., a SeNB). If it isassumed that the RRC connection terminates in the MeNB, then thecomplete message may be received by the RRC entity in the MeNB.

User plane aspects are contemplated. From the perspective of the userplane architecture, the network may terminate S1-u in the MeNB (e.g., inthe MeNB and not the SeNB for one or more, or each, EPS bearers). Thenetwork may terminate (e.g., additionally terminate) S1-u in the SeNB(e.g. for one or more EPS bearer).

Layer 2 (L2) transport of user plane and/or control plane data arecontemplated. From the perspective of the L2 transport of SRB dataand/or user plane traffic, data for a given radio bearer may betransmitted from the network to the WTRU using a single L2 path or usingeither L2 path (hereafter referred to as DL multi-flow). Datatransmitted may be transmitted from the WTRU to the network using asingle L2 path or using either L2 path (e.g., UL multi-flow). Multi-flowmay be realized by configuration of a bearer such that it may be mappedto different cells associated to more than one eNB.

A transport bearer function may be modeled as a combination ofQuality-of-Service (QoS) related aspects and a routing function.QoS-related aspects may be parameterized in terms of (e.g., maximum orguaranteed) bit rate, maximum tolerable latency or the likes. Routingfor a bearer may be achieved using some form of physical or logicalpoint-to-point transport path (e.g., such as using a tunneling functionbased on GTP-u or based on an IP tunnel).

The terms primary MAC entity and Secondary MAC entity may refer to MACentities as separate processes associated (e.g., each associated) tocells of different eNBs (e.g., a MeNB and a SeNB) and to the associatedLayer 1 (L1) or physical layer processing. The terms primary MAC entityand Secondary MAC entity may refer to a single MAC entity which may makethe distinction between a Uu (e.g., L1/PHY) associated to a first eNB(e.g., a MeNB) and to a second eNB (e.g. a SeNB). The WTRU may have oneprimary MAC entity associated to the MeNB and one secondary MAC entityassociated to a SeNB.

The Primary MAC entity may correspond to the MAC entity that isconfigured with the PCell on which the WTRU may have established the RRCconnection (e.g., as per the legacy R10 definition of the PCell). TheSecondary MAC entity may be configured with a special cell, for example,in which case such cell may be configured with an uplink carrier andwith additional PUCCH resources.

Latency reduction may is contemplated.

Pre-allocation of resources are contemplated. Pre-allocation may be aform of pre-scheduling that may provide the WTRU with an opportunity tosend UL packets without requiring the WTRU to send a scheduling request.Pre-allocation may provide resource block grants to WTRUs, for example,in case they have something to transmit when those resource blocks arenot used for actual traffic from other WTRUs. Pre-allocation may bedifferent from other forms of pre-scheduling, such as semi-persistentscheduling. Pre-allocation may use the PDCCH to grant UL resources whennot used by actual traffic. Semi-persistent scheduling may provide aregular allocation to the WTRU, for example, without repetitivescheduling on the PDCCH.

Contention-Based PUSCH is contemplated. Contention Based (CB)transmission may allow uplink synchronized WTRUs to transmit uplink datawithout sending Scheduling Request in advance. Dynamic assignment ofuplink Resource Blocks for CB transmission may be achieved by using theDownlink Physical Control Channel (PDCCH). By using the PDCCH, CB grantsmay be assigned to unused resources on a per subframe basis, forexample, so that scheduling of uplink CF transmissions is not affected.A static assignment of CB resources may be avoided. CB resources may bedynamically assigned, for example, depending on the uplink load.

Contention Based Radio Network Temporary Identifiers (CB-RNTI) may beintroduced to identify the CB uplink grants on the PDCCH. The CB uplinkgrants may have the same format as for Rel-8 WTRUs, such as ResourceBlocks, Modulation and Coding Scheme and Transport Format to be used forthe uplink CB transmission. Rel-10 WTRUs may listen for CB uplink grantsaddressed to these CB-RNTIs and grants addressed to their dedicatedC-RNTI. The available CB-RNTIs in a cell may be broadcasted or signaledto one or more (e.g., each) WTRU during RRC connection setup. The schememay be backwards compatible, since pre Rel-10 WTRUs might not decode thegrants addressed to CB-RNTIs.

SR-associated contention-based is contemplated. With SR associatedcontention based transmission, pre-allocated resource may be shared andidentification of the WTRUs making use of it may be done via the D-SR.This may save latency associated to the eNB processing time betweenreception of D-SR and issuing a grant for a transmission.

Applicability of the different latency reduction schemes to a subset ofdata is contemplated. To lower the probability of collisions for schemesusing a shared (e.g., or contentious) resource, the WTRU may be allowedto use such resource for transmissions associated to a subset of itsradio bearers (e.g., only for transmissions associated to a subset ofits radio bearers).

L1/2TTI Reduction is contemplated. From the perspective of the physicallayer, latency may be reduced by shortening at least one of thefollowing timing aspects: the Transmission Time Interval (TTI), or theHARQ Round-Trip Time (RTT).

In reduction of the Transmission Time Interval (TTI), the TTI may bereduced by shortening in time one or more types of transmissions, forexample, by using one slot in the legacy subframe instead of both slots.

In reduction of the HARQ Round-Trip Time (RTT), the HARQ RTT may bereduced by adjusting timing relationship between scheduling,transmissions and associated HARQ feedback. This may reduce theprocessing time budget for the WTRU and for the eNB. Reduction of theHARQ Round-Trip Time (RTT) may be combined with TTI length reduction.

Enabling shorter TTIs and/or shorter HARQ RTT for at least sometransmissions and/or for at least some types of transmissions may bedifficult to be made backward compatible. Otherwise, this may be akin tothe design of a new air interface.

L3/2 Connectivity Management is contemplated. From the perspective ofL3/2 connectivity management, latency may be reduced by addressing atleast some of a number of aspects, such as: RRC Connection establishmentprocedure (from RRC IDLE, e.g., when transitioning from IDLE); ECM-IDLEto ECM-CONNECTED; NAS Service Request (SR) procedure (from RRC IDLE,e.g., when in RRC IDLE); and/or security activation (from RRC IDLE,e.g., when transitioning from IDLE).

In RRC Connection establishment procedure (from RRC IDLE), the networkmay keep a WTRU in RRC Connected and/or send the WTRU to RRC IDLE whenit determines that the WTRU is no longer active, for example, based onthe expiration of an inactivity timer managed by the eNB. There may be atradeoff between both approaches in terms of mobility management,signaling overhead and latency before the WTRU may become active intransmissions after a period of inactivity. This bottleneck may beaddressed, for example, by enabling certain data transfers without theneed for an established (e.g., or up-to-date) RRC connection and/or byestablishing intermediate connectivity state in the RAN. This may beaccomplished by modeling additional state(s) in the RRC protocol (e.g.,an RRC-Inactive state).

In ECM-IDLE to ECM-CONNECTED, from the WTRU's perspective, the ECM statemay follow the RRC state. In ECM-IDLE to ECM-CONNECTED, from the MME'sperspective, the ECM state may depend on S1 connection state (e.g., oneof established or released). Latency may be reduced by decoupling theMME state from the RRC state, for example, at least partially. This maybe accomplished by modeling additional state(s) in the RRC protocol(e.g., an EMM-Inactive state). In such case, ensuring that the S1connection may follow the WTRU may be difficult, for example, in case ofWTRU autonomous mobility (e.g., cell reselection).

In NAS Service Request (SR) procedure (from RRC IDLE), the WTRU may sendan NAS SR to establish, for example, a DEFAULT bearer and/or when abearer with higher Quality of Service (QoS) may be utilized. Thisprocedure may utilized the involvement from the core network and/orintroduce additional latency, for example, when the WTRU performs theinitial RRC Connection establishment procedure. This may be avoided, forexample, by enabling means for the WTRU and the network to maintain theEPS bearer independently of the state of the associated DRB (e.g., basedon the modeling of an ECM-Inactive state) and/or independently of thestate of the RRC Connection (e.g., based on the modeling of anRRC-Inactive state).

In security activation (from RRC IDLE), the WTRU may have a validsecurity context for the lifetime of the RRC Connection. Security may beactivated when the WTRU performs the initial RRC ConnectionEstablishment procedure, for example, when moving from RRC IDLE to RRCCONNECTED state. At least parts of a security context from one RRCconnection to another may be maintained or reused. Such security contextmay be valid beyond the RRC CONNECTED state and may continue in adifferent RRC state (e.g., based on the modeling of an RRC-Inactivestate).

PRACH Resource multiplexing is contemplated. In LTE R8/9/10+, the WTRUmay initiate the RA procedure when one of the following events occurs: aconnection establishment, for example, when the WTRU accesses thenetwork to establish an RRC connection; a mobility event, when the WTRUaccesses the target cell during a handover procedure; a recovery event,when the WTRU performs the RRC Connection Re-establishment procedure; anetwork-initiated, when instructed by the NW (e.g., by PDCCH RA order)for example, for DL data arrival; a scheduling request (RA-SR), when theWTRU has new UL data to transmit and the data is of higher priority thanexisting data in its buffer, and the WTRU has no D-SR.

The RA procedure may be either contention-free (CFRA) orcontention-based (CBRA), for example depending on whether or not theWTRU is assigned dedicated RACH resources, either a specific preambleand/or a resource on the Physical Random Access Channel (PRACH). The RAprocedure may consist of the following: MSG0 (e.g., when networkinitiated), comprising the DCI received on PDCCH indicates RACH may beperformed; MSG1, comprising preamble transmission on a resource of thePRACH; MSG2, comprising Random Access Response (RAR) reception; MSG3,comprising transmission of message3, which may contain a BSR, signalingdata and/or user-plane data; and MSG4, comprising contention resolution,such as the WTRU determining whether or not it successfully completedthe RACH procedure based on either C-RNTI on PDCCH or WTRU ContentionResolution Identity on DL-SCH. The RAR may comprising an uplink grantand a Timing Advance Command (TAC);

For CBRA, in LTE, there may be a PRACH (e.g., at most one PRACH)configured for a given cell, such as there may be a single set of PRACHresources in a cell.

For FDD, a WTRU may be configured by higher layer configuration (e.g.,either from reception of broadcasted System Information or fromreception of dedicated signaling) a PRACH (e.g., with at most one PRACH)for any given subframe that may be configured with available PRACHresources.

For TDD, due to the nature of the UL/DL subframe configuration,frequency multiplexing may be used when time multiplexing may beinsufficient to obtain the desired PRACH density. In this case, the WTRUmay be configured by higher layer configuration (e.g., either fromreception of broadcasted System Information and/or from reception ofdedicated signaling) with multiple PRACH resources for one or more(e.g., each) subframe configured with available PRACH resources. One ormore (e.g., each) PRACH resource may be indexed, for example, based onincreasing frequency domain. In other words, when frequency multiplexingis used, there may be multiple (e.g., multiples of six) PhysicalResource Blocks (PRBs) for PRACH availability in the given subframe,where on or more (e.g., each) group (e.g., group of six) PRBs representsa single PRACH opportunity.

The WTRU may transmit a preamble on a configured uplink resource forPRACH, for example, if such resource is available in the given subframe,such as when the WTRU performs the random access procedure. One or more(e.g., each) random access preamble may occupy a bandwidth correspondingto one or more (e.g., six) consecutive PRBs for both FDD and TDD.

Existing PRACH resources may be partitioned (e.g. based on timing,preamble groups) and/or PRACH resources may be multiplexed (e.g. in thetime domain, in the frequency domain or both in combination).

One or more design approaches for 5G systems are contemplated. One ormore flexible radio accesses for 5G are contemplated. Mobilecommunications are in continuous evolution and is already at thedoorstep of its fifth incarnation—5G. New use cases may contribute insetting the requirements for the new system. It is expected that the 5Gair interface may at least enable the following use cases:

-   -   Improved broadband performance (IBB);    -   Industrial control and communications (ICC) and vehicular        applications (V2X); and/or    -   Massive Machine-Type Communications (mMTC).        Theses uses cases, among others, may be translated into one or        more of the requirements for the 5G interface described herein.

Support for Baseband filtering of frequency-domain waveform iscontemplated. At least one design consideration may be the ability forbaseband filtering of the frequency-domain waveform to enable effectiveaggregation of up to 150-200 MHz total spectrum, perhaps for examplewithin a given RF transceiver path, and/or perhaps for example withoutrelying on a re-design of the front end.

Aggregation of spectrum across widely separated operating bands (e.g.900 MHz and 3.5 GHz) may still use multiple RF transceiver chains,perhaps for example because of antenna size requirements and/oramplifier optimization design constraints. A WTRU/UE implementation mayinclude up to three or more separate RF transceiver paths, for example:a first one below 1 GHz, a second one for the 1.8-3.5 GHz frequencyrange, and/or a third one covering the 4-6 GHz frequency range.

Native built-in support for Massive MIMO antenna configurations may be asecond order requirement.

It may be useful for at least IBB that multiple frequency bands withspectrum of varying sizes be efficiently aggregated, perhaps for exampleto achieve data rates in the order of several tens of Mbps (e.g., celledge) up to peak data rates of several Gbps (e.g. up to 8 Gbps) withtypical rates perhaps for example in the order of several hundreds ofMbps.

Support for ultra-low transmission latency is contemplated. Airinterface latency as low as 1 ms RTT may use support for TTIs, forexample somewhere between 100 us and 250 us (perhaps for example nolarger than 250 us).

Support for ultra-low access latency (e.g. time from initial systemaccess until the completion of the transmission of the first user planedata unit) is contemplated.

It may be useful for at least ICC and/or V2X to experience end-to-end(e2e) latency of less than 10 ms, for example.

Support for ultra-reliable transmission is contemplated. At least onedesign consideration may be to improve transmission reliability comparedto what is possible with legacy LTE systems. For example, suchimprovement could target a 99.999% transmission success and/or serviceavailability. Another consideration may be support for mobility forspeed in the range of 0-500 km/h. It may be useful for at least ICCand/or V2X to experience Packet Loss Rate of less than 10e⁻⁶.

Support for MTC operation (e.g., including narrowband operation) iscontemplated. The air interface may (e.g., efficiently) supportnarrowband operation (e.g. using less than 200 KHz). Extend battery life(e.g. up to 15 years of autonomy) is contemplated. Minimal communicationoverhead for small and/or infrequent data transmissions (e.g. low datarate in the range of 1-100 kbps with access latency of seconds to hours)is contemplated.

Support for mMTC use cases may utilize narrowband operation. Theresulting link budget may be comparable to that of LTE extendedcoverage, perhaps for example while supporting a (e.g., very large)number of MTC devices (e.g., up to 200 k/km²) perhaps without adverseimpact on spectral efficiency for other supported services.

One or more of the design considerations described herein can beincluded into one or more design aspects described herein.

It may be useful for the 5G system design to enable flexible spectrumusage, deployment strategies, and/or operation.

The design may support operation using spectrum of varying size,including aggregation of non-adjacent carriers in the same and/or indifferent frequency bands, licensed, and/or unlicensed. The system maysupport narrowband and/or wideband operation, different duplexingmethods (e.g., for TDD, dynamically variable DL/UL allocation), variableTTIs lengths, scheduled and/or unscheduled transmissions, synchronousand/or asynchronous transmissions, separation of user plane from thecontrol plane, and/or multi-node connectivity.

The 5G system design integrating with a number of legacy (E-)UTRAN andEPC/CN aspects is contemplated.

Although there is no requirement for backward compatibility, the systemmay integrate and/or operate with one or more legacy interfaces (e.g.,or evolution thereof) at least towards the legacy CN (e.g. the S1interface, NAS) and/or eNBs (e.g. the X2 interface including dualconnectivity with LTE), perhaps for example to enable legacy aspectssuch as support for existing QoS and/or security mechanisms.

Specific elements of the 5G design could be retrofitted in LTE Evolution(e.g. backward compatibility of some or all components are alsoconsidered). For example, TTIs shorter than a LTE slot (e.g., 0.5 ms)using a different waveform to enable ultra-low latency are contemplated.For example, operating the 5G physical layer (e.g., DL and/or UL) in TDMand/or in FDM with LTE.

One or more of the following functionality that may be supported bylegacy systems is contemplated: Support for D2D/Sidelink operation;Support for LAA operation using LBT; and/or Support for relaying.

One or more (e.g., basic) principles for the Flexible Radio AccessSystem for 5G—The 5gFLEX—are contemplated.

OFDM may be used as the (e.g., basic) signal format for datatransmissions in LTE and/or in IEEE 802.11. OFDM may efficiently dividethe spectrum into one or more, or multiple, parallel orthogonalsubbands. One or more, or each, subcarrier may be shaped using arectangular window in the time domain that may for example lead tosinc-shaped subcarriers in the frequency domain. OFDMA may use (e.g.,perfect) frequency synchronization and/or tight management of uplinktiming alignment, perhaps for example within the duration of the cyclicprefix to maintain orthogonality between signals and/or to minimizeintercarrier interference. Such tight synchronization might not bewell-suited in a system where a WTRU may be connected to multiple accesspoints simultaneously. Additional power reduction may also be applied touplink transmissions perhaps for example to comply with spectralemission requirements to adjacent bands (perhaps for example inparticular in the presence of aggregation of fragmented spectrum for theWTRU's transmissions).

Some of the shortcomings of conventional OFDM (CP-OFDM) can be addressedby more stringent RF requirements for implementations, perhaps forexample when operating using a large amount of contiguous spectrum thatmight not use aggregation. A CP-based OFDM transmission scheme may leadto a downlink physical layer for 5G, perhaps for example similar to thatof legacy system (e.g. mainly modifications to pilot signal densityand/or location).

The 5gFLEX design may consider other waveform candidates, althoughconventional OFDM remains a possible candidate for 5G systems, perhapsfor example at least for the downlink transmission scheme.

One or more principles behind the design of a flexible radio access for5G are described herein. One or more transmission schemes arecontemplated.

The 5gFLEX downlink transmission scheme may be based on a multicarrierwaveform characterized by high spectral containment (e.g., lower sidelobes and/or lower OOB emissions). Possible MC waveform candidates for5G include OFDM-OQAM and UFMC (UF-OFDM).

Multicarrier modulation waveforms may divide the channel into one ormore subchannels and/or modulate data symbols on subcarriers in theseone or more subchannels.

With OFDM-OQAM, a filter may be applied in the time domain persubcarrier to the OFDM signal, perhaps for example to reduce OOB.OFDM-OQAM may cause (e.g., very) low interference to adjacent bands,might not use large guard bands, and/or might not use a cyclic prefix.OFDM-OQAM may be a popular FBMC technique, but may be sensitive tomultipath effects and/or to high delay spread in terms of orthogonality,thereby complicating equalization and/or channel estimation.

With UFMC (UF-OFDM), a filter may be applied in the time domain to theOFDM signal, perhaps for example to reduce OOB. Filtering may be appliedper subband to use spectrum fragments that may reduce complexity and/ormake UF-OFDM somewhat more practical to implement. Perhaps for exampleif there are unused spectrum fragment in the band, OOB emissions inthese fragments may remain as high as for conventional OFDM. In otherwords, UF-OFDM may improve over OFDM at the edges of the filteredspectrum (e.g., perhaps for example at the edges only, and not in thespectral hole).

Techniques described herein might not be limited to the aforementionedwaveforms and/or may be applicable to other waveforms. Theaforementioned waveforms may be further used for example purposes.

Such waveforms may enable multiplexing in frequency of signals withnon-orthogonal characteristics (e.g., such as different subcarrierspacing) and/or co-existence of asynchronous signals, perhaps forexample without requiring complex interference cancellation receivers.It may facilitate the aggregation of fragmented pieces of spectrum inthe baseband processing as a lower cost alternative to itsimplementation as part of the RF processing.

Co-existence of different waveforms within the same band is considered,perhaps for example at least to support mMTC narrowband operation (e.g.using SCMA), among other scenarios. Another example is of supportingwithin the same band, the combination of different waveforms (e.g.CP-OFDM, OFDM-OQAM and UF-OFDM) for one or more, or all, aspects, and/orfor downlink and/or uplink transmissions. Such co-existence may includetransmissions using different types of waveforms between different WTRUsor transmissions from the same WTRU (e.g. either simultaneously, withsome overlap, and/or consecutive in the time domain).

Further co-existence aspects may include support for hybrid types ofwaveforms (e.g. waveforms and/or transmissions that support at least oneof a possibly varying CP duration (e.g. from one transmission toanother)), a combination of a CP and a low power tail (e.g. a zerotail), and/or a form of hybrid guard interval (e.g. using a low power CPand an adaptive low power tail), and/or the like. Such wavefroms maysupport dynamic variation and/or control of further aspects, such as howto apply filtering (e.g. whether filtering is applied at the edge of thespectrum used for reception of any transmission(s) for a given carrierfrequency, at the edge of a spectrum used for reception of atransmission associated to a specific SOM, per subband, and/or per groupthereof).

The uplink transmission scheme may use a same and/or different waveformas for downlink transmissions. Multiplexing of transmissions to and/orfrom different WTRUs in the same cell may be based on FDMA and/or TDMA.

Uplink non-orthogonal transmissions may also be supported. One or more,or multiple, WTRUs may perform a transmission in the same set ofresources, perhaps for example when the receiver in the network sideimplements advanced receiver technologies such as SIC (SuccessiveInterference Cancellation), among other scenarios. For example,transmissions from different WTRUs may be spread over one or more, ormultiple, PRBs. A (e.g., very) low MCS may be used as a form ofspreading technique and/or WTRU-specific hopping may be used to maximizefrequency and/or interference diversity. Transmissions may use aWTRU-specific DM-RS (e.g. for demodulation and/or decoding, and/or todetermine the identity of the WTRU that performed the transmission).Such transmissions may be useful for (e.g., relatively small) datapackets. Different WTRUs may perform uplink transmission in adjacentresources in frequency and/or in time, perhaps for example without tighttiming synchronization. Such transmission methods may enable a WTRU toperform uplink transmissions, perhaps for example without having tofirst receive a grant from the network.

Spectrum Flexibility is contemplated. The 5gFLEX radio access design maybe characterized by a (e.g., relative very) high degree of spectrumflexibility that may enable deployment in different frequency bands withdifferent characteristics. The characteristics may include differentduplex arrangements, different and/or variable sizes of the availablespectrum including contiguous and/or non-contiguous spectrum allocationsin the same and/or different bands. Variable timing aspects includingsupport for multiple TTI lengths and/or support for asynchronoustransmissions may be supported.

Flexibility in Duplexing Arrangement is contemplated. TDD and/or FDDduplexing schemes may be supported. For FDD operation, supplementaldownlink operation may be supported, perhaps for example using spectrumaggregation. FDD operation may support full-duplex FDD and/orhalf-duplex FDD operation. For TDD operation, the DL/UL allocation maybe dynamic (e.g., it might not be based on a fixed DL/UL frameconfiguration). The length of a DL and/or a UL transmission interval maybe set per transmission opportunity.

Bandwidth Flexibility is contemplated. At least one characteristic ofthe 5gFLEX design is the possibility for different transmissionbandwidths on uplink and/or downlink, perhaps for example ranging fromanything between a nominal system bandwidth up to a maximum valuecorresponding to the system bandwidth.

For single carrier operation, the supported system bandwidths mayinclude at least 5, 10, 20, 40 and/or 80 MHz. Supported systembandwidths could be any bandwidth in a given range (e.g. from a few MHzup to 160 MHz). Nominal bandwidths could possibly have one or morepossible values (e.g., fixed). Narrowband transmissions of up to 200 KHzmay be supported within the operating bandwidth for MTC devices.

In one or more techniques, system bandwidth as used herein may refer tothe largest portion of spectrum that can be managed by the network for agiven carrier. For such a carrier, the portion that a WTRU may (e.g.,minimally) support for cell acquisition, measurements, and/or initialaccess to the network may correspond to the nominal system bandwidth.The WTRU may be configured with a channel bandwidth that may be withinthe range of the entire system bandwidth. The WTRU's configured channelbandwidth may, or might, not include the nominal part of the systembandwidth as shown in FIG. 2.

Bandwidth flexibility can be achieved because one or more, or all,applicable set of RF requirements for a given maximum operatingbandwidth in a band can be met, perhaps for example without theintroduction of additional allowed channel bandwidths for that operatingband. This may be due, at least in part, to the efficient support ofbaseband filtering of the frequency domain waveform.

The 5gFLEX physical layer may be band-agnostic and/or may supportoperation in licensed bands below 5 GHz and/or operation in theunlicensed bands in the range 5-6 GHz. For operation in the unlicensedbands, LBT Cat 4 based channel access framework similar to LTE LAA maybe supported.

Flexible Spectrum Allocation is contemplated. Downlink control channelsand/or signals may support FDM operation. A WTRU can acquire a downlinkcarrier, for example, by receiving transmissions using (e.g., usingonly) the nominal part of the system bandwidth (e.g., the WTRU might notinitially receive transmissions covering the entire bandwidth that isbeing managed by the network for the concerned carrier).

Downlink data channels can be allocated over a bandwidth that may ormight not correspond to the nominal system bandwidth, perhaps forexample without restrictions other than being within the WTRU'sconfigured channel bandwidth. For example, the network may operate acarrier with a 12 MHz system bandwidth using a 5 MHz nominal bandwidth.This may allow devices supporting (e.g., at most) 5 MHz maximum RFbandwidth to acquire and/or access the system, perhaps for example whileallocating +10 to −10 MHz of the carrier frequency to other WTRU's thatmay be supporting up to 20 MHz, or more, worth of channel bandwidth.

FIG. 3 shows an example of spectrum allocation where differentsubcarriers may be at least conceptually assigned to different modes ofoperation (hereafter “SOM”). Different SOM can be used to fulfilldifferent requirements, perhaps for example for different transmissions.A SOM may include at least one of: a subcarrier spacing, a TTI length,and/or one or more reliability aspects (e.g. HARQ processing aspectsand/or a secondary control channel). A SOM may be used to refer to aspecific waveform and/or may be related to a processing aspect (e.g. insupport of co-existence of different waveforms in the same carrier usingFDM and/or TDM, and/or in scenarios such as those in which thecoexistence of FDD operation in a TDD band is supported (e.g. in a TDMmanner or similar)).

Spectrum Aggregation is contemplated. For single carrier operation,spectrum aggregation may be supported, such that the WTRU may supporttransmission and/or reception of multiple transport blocks, perhaps forexample over contiguous and/or non-contiguous sets physical resourceblocks (PRBs), perhaps for example within the same operating band.Mapping of a single transport block to separate sets of PRBs iscontemplated.

Support for simultaneous transmissions associated to different SOMrequirements is contemplated. Multicarrier operation may be supported,perhaps for example by using contiguous and/or non-contiguous spectrumblocks, perhaps for example within the same operating band and/or acrosstwo or more operating bands. Aggregation of spectrum blocks usingdifferent modes (e.g., FDD and TDD) and/or using different channelaccess methods (e.g., licensed and/or unlicensed band operation below 6GHz) may be supported.

Support for methods that configure, reconfigure, and/or dynamicallychange the WTRU's multicarrier aggregation is contemplated. Such highflexibility for spcctrum aggregation might not require RF specificationwork to support additional channels and/or band combinations, perhapsfor example because the use of efficient baseband filtering in thefrequency domain.

Flexible Framing, Timing, and/or Synchronization are contemplated.Downlink and/or uplink transmissions may be organized into radio framescharacterized by a number of fixed aspects (e.g. location of downlinkcontrol information) and/or a number of varying aspects (e.g.transmission timing and/or supported types of transmissions).

The basic time interval (BTI) may be expressed in terms of an integernumber of one or more symbol(s). Symbol duration may be a function ofthe subcarrier spacing applicable to the time-frequency resource. ForFDD, subcarrier spacing may differ between the uplink carrier frequencyfUL and/or the downlink carrier frequency fDL for a given frame, forexample.

A transmission time interval (TTI) may be the minimum time supported bythe system between consecutive transmissions where one or more, or each,may be associated to different transport blocks (TBs) for the downlink(TTIDL), for the uplink (UL TRx) perhaps excluding any preamble (e.g.,if applicable) and/or perhaps including any control information (e.g.DCI for downlink or UCI for uplink). A TTI may be expressed in terms ofinteger number of one or more BTI(s). A BTI may be specific and/orassociated to a given SOM.

Supported frame duration may include 100 us, 125 us (1/8 ms), 142.85 us(1/7 ms is 2 nCP LTE OFDM symbols) and/or 1 ms, perhaps for example toenable alignment with the legacy LTE timing structure.

Fixed framing aspects are contemplated. A frame starts (e.g., perhapsalways starts) with downlink control information (DCI) of a fixed timeduration t_(dci) that may precede any downlink data transmission (DLTRx) for the concerned carrier frequency—fUL+DL for TDD and/or fDL forFDD.

For TDD duplexing (e.g. perhaps for TDD duplexing only), a frame mayinclude a downlink portion (DCI and/or DL TRx) and/or an uplink portion(UL TRx). A switching gap (swg) may precede (e.g., perhaps may alwaysprecede) the uplink portion of the frame (e.g., if present).

For FDD duplexing (e.g., perhaps FDD duplexing only), a frame mayinclude a downlink reference TTI and/or one or more TTI(s) for theuplink. The start of an uplink TTI may be derived (e.g., perhaps mayalways be derived) using an offset (toffset) applied from the start ofthe downlink reference frame that overlaps with the start of the uplinkframe.

For TDD, 5gFLEX may support D2D/V2x/Sidelink operation in the frame byincluding respective downlink control and/or forward directiontransmission in the DCI+DL TRx portion (e.g., perhaps if a semi-staticallocation of the respective resources may be used) and/or in the DL TRxportion (e.g., perhaps in the DL TRx portion only and/or for dynamicallocation) and/or by including the respective reverse directiontransmission in the UL TRx portion.

For FDD, 5gFLEX may support D2D/V2x/Sidelink operation in the UL TRxportion of the frame perhaps for example by including respectivedownlink control, forward direction, and/or reverse directiontransmissions in the UL TRx portion (e.g., dynamic allocation of therespective resources may be used). An example frame structure and timingrelationships are shown in FIG. 4 (TDD) and/or FIG. 5 (FDD).

Scheduling and/or Rate Control is contemplated. A scheduling functionmay be supported in the MAC layer. At least two scheduling modes may besupported: network-based scheduling for tight scheduling in terms ofresources, timing and transmission parameters of downlink transmissions,and/or uplink transmissions; and WTRU-based scheduling for moreflexibility in terms of timing and transmission parameters. For oneand/or both modes, scheduling information may be valid for a single orfor multiple TTIs.

Network-based scheduling is contemplated. Network-based scheduling mayenable the network to tightly manage the available radio resourcesassigned to one or more, or different, WTRUs such as to optimize thesharing of such resources. Dynamic scheduling may be supported.

WTRU-based scheduling is contemplated. WTRU-based scheduling may enablethe WTRU to opportunistically access uplink resources with minimallatency on a per-need basis, perhaps for example within a set of sharedand/or dedicated uplink resources assigned (e.g., dynamically or not) bythe network. Synchronized and/or unsynchronized opportunistictransmissions may be supported. Contention-based transmissions and/orcontention-free transmissions may be supported.

Support for opportunistic transmissions (e.g., scheduled and/orunscheduled) may be included to meet the ultra-low latency requirementsfor 5G and/or the power saving requirement of the mMTC use case.

Logical Channel Prioritization is contemplated. 5gFLEX may support theassociation of data available for transmission and/or availableresources for uplink transmissions. Multiplexing of data with differentQoS requirements, perhaps for example within the same transport blockmay be supported, perhaps for example as long as such multiplexingneither introduces negative impact to the service with the moststringent QoS requirement, nor introduces unnecessary waste of systemresources, among other scenarios.

Forward Error Correction (FEC) and/or Block Coding are contemplated. Atransmission may be encoded using a number of different encodingmethods. Different encoding methods may have different characteristics.For example, an encoding method may generate a sequence of informationunits. One or more, or each, information unit, or block, may beself-contained. For example, an error in the transmission of a firstblock might not impair the ability of the receiver to successfullydecode a second block, perhaps for example if the second block may beerror-free and/or if sufficient redundancy can be found in the secondblock and/or in a different block for which at least a portion wassuccessfully decoded.

Examples of encoding methods include raptor/fountain codes in which atransmission may include a sequence of N raptor codes. One or more suchcodes may be mapped to one or more transmission “symbols” in time, forexample. A “symbol” can correspond to one or more set of informationbits (e.g. one or more octets). Such encoding may be used to add FEC toa transmission. The transmission could use N+1 and/or N+2 raptor codes(e.g. and/or symbols, perhaps assuming a one raptor code symbolrelationship) so that the transmission may be more resilient to the lossof one “symbol” (e.g. perhaps due to interference and/or puncturing byanother transmission overlapping in time).

The minimization of time between data becoming available fortransmission until the WTRU may first become active in transmission forthat data is contemplated. The reduction of transmission latency fordata either in the eNB for downlink transmissions or in the WTRU foruplink transmissions is contemplated.

The following cases are contemplated, for example, focusing on L2aspects, such as unsynchronized access (e.g., applicable to RRC IDLEand/or RRC CONNECTED) and synchronized access (e.g., applicable to RRCCONNECTED).

In unsynchronized access (e.g., applicable to both RRC IDLE or RRCCONNECTED), an unsynchronized access may be characterized, at least inpart, such that the WTRU may have an invalid uplink timing alignment fora serving cell or for a group of serving cells for which it may use toaccess uplink resources. In this case, the primary contributor (e.g., orbottleneck) to latency may be related to the performance of the randomaccess procedure to gain at least uplink timing alignment, such that theWTRU may subsequently perform uplink transmissions on dedicatedresources (e.g. transmission of Uplink Control Information (UCI) onPUSCH or PUCCH, which UCI may include HARQ ACK/NACK related to thereception of downlink data) and/or transmission of uplink data on PUSCH.

For a WTRU in RRC IDLE mode, perhaps for example independently ofwhether transmissions are triggered by downlink data arrival (e.g., theWTRU receives paging) and/or by uplink data arrival (e.g., the WTRUinitiates one or more procedures to acquire uplink resources such as forexample, the RA-SR procedure in LTE, among other techniques), it may beuseful to reduce the latency of the initial access. It may be useful inLTE to reduce latency of one or more of the (e.g., contention-based)random access procedure (e.g., for uplink timing alignment, initialpower setting, C-RNTI allocation), the RRC Connection establishmentprocedure (e.g., for NAS and EPS bearer setup, L2/L3 configuration,security activation), and/or the scheduling of the first data packet forthe service (e.g., or bearer) from reception of a grant for uplink dataand/or from reception of a downlink assignment for downlink data may bedifficult.

For a WTRU in RRC CONNECTED mode, reducing the latency of the randomaccess procedure (e.g., initiated by RA-SR for uplink data arrival or byPDCCH reception for downlink data arrival) and/or the scheduling of thefirst data packet for the burst of data for a configured service (e.g.,or bearer) are contemplated. Mobility when (e.g., first) accessing atarget cell is contemplated.

Techniques to reduce latency may focus on reducing the latencyassociated with the random access procedure. In particular for RRC IDLEmode, such methods may be used in combination with other methods such asthose described herein, e.g. methods that may reduce (e.g., or removethe need for) latency of the RRC Connection establishment procedureand/or the bearer setup and/or security activation procedure.

In synchronized access (e.g., RRC CONNECTED), a synchronized access maybe characterized, at least in part, such that the WTRU has a validuplink timing alignment for a serving cell or for a group of servingcells for which it may utilize to access uplink resources. In this case,the challenge for uplink data arrival may be to reduce the latency forthe WTRU to get access to a dedicated resource for uplink transmissions,for example, on PUSCH. The primary contributor (e.g., or bottleneck) tolatency may be the average time between occasions for performingscheduling request (SR), for example, by transmission of SR on adedicated PUCCH resource (e.g., D-SR, if configured) or SR on PRACH(e.g., RA-SR, otherwise) and/or for performing a CB-PUSCH transmission(e.g., if such is configured and/or available). There may be a tradeoffbetween D-SR density, PRACH density and CB-PUSCH density and latencywhich comes to a cost in terms of resource usage. The challenge fordownlink data arrival may be the tradeoff between power efficiency andPDCCH monitoring for DL assignments, for example, based on aDiscontinuous Reception (DRX) algorithm (e.g., if configured).

The latency bottlenecks may be identified herein with their respectivepossible aspects to be addressed. A bottleneck may be a place wherelatency may be reduced and time may be saved with appropriate proceduresor changes to existing procedures.

A bottleneck may occur at paging (e.g., RRC IDLE, DL data arrival).Extended paging may be in parallel with legacy paging. In this case, oneissue to be addressed may be how to tell the WTRU that it should accessthe system faster than with legacy paging and connection establishmentprocedures. Extended paging with WTRU-controlled UL synchronization mayenable grant. One issue to be addressed in this case may be how toenable an extension to the paging mechanism that may provide means forthe WTRU to acquire uplink resources (e.g., dedicated grant or CB-PUSCHif synchronized state is available in RRC IDLE mode) and to transmituser plane data already in the first response to the paging request.And, if so, under what circumstances. Extended paging may triggerconnection reactivation/re-establishment. One issue to be addressed inthis case may be how to enable an extension to the paging mechanism thatmay provide means for the WTRU to perform some form of reconnection orreactivation of an existing and/or of a previous connection. IfNW-based, paging may or might not include contextual information inaddition to the WTRU's identity in the paging message. If WTRU-based,the response to paging may or might not include contextual informationin addition to (e.g., or instead of) the connection establishmentrequest, for example, using similar principles to the RRC Connectionre-establishment procedure. And, if so, under what circumstances.

A bottleneck may occur in the random Access procedure (e.g.,unsynchronized cases). For example, in WTRU-controlled ULsynchronization, when unsynchronized and/or when not actively managed bythe eNB's scheduler, how a WTRU may acquire (e.g., or maintain) uplinksynchronization and/or initial power level other than using RACH may beaddressed. Examples in which the WTRU transmits data without havingacquired uplink synchronization, and/or which may utilized protection intime to avoid interference with other transmissions in the cell, may bedeemed costly.

A bottleneck may occur in the access to uplink resources includingScheduling Request. Techniques contemplate how to efficiently requestresources for uplink transmissions with minimal latency, for example,for dedicated transmissions and/or contention-based transmissions.Techniques contemplate how to efficiently access uplink transmissionresources with minimal latency, for example, using methods such assemi-persistent allocation (SPS), pre-allocation, and/orcontention-based uplink transmission channel.

Examples described herein may be backward compatible with legacysystems.

Examples are contemplated that reduce the latency for a WTRU to becomeactive with data transmissions. These examples may be usedindependently, in combination with each other and/or in combination withother existing methods.

As described herein, the WTRU may be synchronized, for example, if ithas valid uplink timing alignment and unsynchronized, for example, if itdoes not have a valid uplink timing alignment.

Examples to determine applicable functionality are contemplated. TheWTRU may determine whether or not it uses the techniques describedherein based on one or more, or a number, of criteria. One suchcriterion may be the RRC state (e.g., IDLE, CONNECTED, and/or beinginactive in transmission for a, perhaps specific, amount of time). Forexample, a criterion may be support for the functionality usingresources associated with a given cell (e.g., such as determined fromthe reception of broadcasted system information). For example, acriterion may be configuration aspects of the WTRU.

For a 5gFLEX system, or for further evolutions of the LTE system thatmay support similar functions as the 5gFLEX design approaches,applicability of one or more contemplated techniques may be a functionof the SOM associated to a specific set of uplink resources. Theapplicability may be a function of the set and/or subset of theavailable resources, and/or of one of more characteristic(s) thereof,such as a type of associated control channel and/or any other aspectsassociated to the SOM as described herein. For example, a set ofresources may be associated to a SOM that may support: transmissionsusing a TTI, perhaps for example not exceeding a specific duration (e.g.a TTI of some 100 μs duration); unscheduled and/or contention-basedtransmissions; non-orthogonal transmissions between different WTRUs;and/or a transmission method that might not require strict uplink timingsynchronization (e.g. such as using a filtered type of waveform or thelikes).

A configuration aspect may comprise RRC CONNECTED/Inactive mode anddedicated signaling. For example, a WTRU in RRC CONNECTED mode maydetermine that one or more of the examples described herein may beapplicable if configured by the network. Such configuration may bereceived by dedicated signaling. For example, the WTRU in RRC CONNECTEDmode may be configured using dedicated signaling to operate autonomouslywith the synchronization channel, such as RSSC described herein and/orDSS described herein. Such signaling and/or such configuration may beapplicable for a WTRU in RRC-Inactive mode, for example, perhaps if suchcontrol signaling may be received in such a mode and/or perhaps if theWTRU was configured by the network prior to moving to that state.

For example, the WTRU in RRC CONNECTED mode may receive a RRC ConnectionReconfiguration message with the mobilityControlInformation indicatingthat the WTRU may be expected to perform a change of serving cell. Suchsignaling may indicate that one or more of the techniques describedherein may be applicable to the procedure. Such reconfiguration may befor a mobility procedure and/or for a reconfiguration of a secondarycell group (SCG) with dual connectivity (e.g. a change in PSCell for theSCG).

A configuration aspect may comprise RRC IDLE/Inactive mode andbroadcasted signaling. For example, a WTRU in RRC IDLE mode maydetermine that one or more of the examples described herein may beapplicable, for example, if supported and/or configured by the network.Such support information and/or configuration may be received bybroadcasted signaling. For example, the WTRU in RRC IDLE mode mayreceive a configuration on a broadcast channel such that it may operateautonomously with the synchronization channel, such as RSSC describedherein and/or DSS described herein. Such signaling and/or suchconfiguration may be applicable for a WTRU in RRC-Inactive mode, if suchcontrol signaling may be received in such mode or if the WTRU wasconfigured by the network prior to moving to that state or if the WTRUhas moved to a different cell since it last received control signalingfrom the network.

A configuration aspect may comprise details on what may becell-specific. Such configuration may be WTRU-specific or cell-specific.For example, configuration aspects that may be cell-specific includes,for example, support of extended paging functionality described herein,support and/or configuration of a synchronization channel, such as RSSCdescribed herein and/or DSS described herein, support and/orconfiguration of pre-allocation or CB-PUSCH resources as describedherein and may be received on the System Information Broadcast channel.In particular, such cell-specific information may be applicable forWTRUs in RRC IDLE mode (e.g., or for WTRU's in RRC-Inactive mode).

Extended paging functionality is contemplated. The combination of pagingand immediate data transfer for a synchronized, IDLE/Inactive WTRU maybe enabled. Such paging may be scheduling DL data for short datatransfer (e.g., and/or (e)BSR) such as described herein) directly (e.g.,HARQ A/N is possible) and/or L3 RRCconfiguration/reactivation/reconnection and/or may be granting uplinkresources, such as for L3 RRC reactivation/reconnection request.

For example, the WTRU may use a paging mechanism such that the WTRU maymonitor for downlink control signaling at specific occasions. Suchpaging occasion may be determined based on whether the legacy pagingfunction may be used (e.g., extensions thereof as described herein) or aparallel paging function is used (e.g., such as described herein).

The structure of control signaling for extended paging functionality,for example, DCI/RNTI+PDSCH, DCI/RNTI+(CB-)grant, is contemplated. Suchdownlink control signaling may be at least one of the following: similarto legacy P-RNTI reception, in particular for extended paging; WTRU, orgroup-specific RNTI reception, for example based on configuration, onthe DL; WTRU, or group-specific RNTI reception, for example based onconfiguration, on the UL.

In similar to legacy P-RNTI reception, in particular for extendedpaging, a DCI received on PDCCH (e.g., using P-RNTI) may indicate that apaging message is transmitted on the PDSCH. For example, such pagingmessage may include extended information and/or control signaling (e.g.,such as described herein).

For a WTRU, or group-specific RNTI reception, for example, based onconfiguration, in the DL, a DCI received on PDCCH (e.g., using a RNTIspecific to the WTRU) may indicate that a transport block addressed tothe WTRU is transmitted on the PDSCH. For example, such transport blockmay include data for the WTRU. For example, such data may be user planedata (e.g., for short downlink data transfers). For example, such datamay consist of control signaling (e.g., such as described herein). Ifthe transmission is for a specific WTRU, the WTRU may transmit HARQfeedback, for example, as described herein.

For WTRU, or group-specific RNTI reception, for example based onconfiguration, on the UL, a DCI received on PDCCH may indicate that agrant for an uplink transmission is available to the WTRU on (CB-)PUSCH. For example, the WTRU may be configured with a RNTI to thispurpose. Such RNTI may be WTRU-specific, for example, such as a RNTIassigned to the WTRU using dedicated signaling. In such case, thenetwork may assign the same RNTI to a plurality of WTRUs. For example,the network may allocate the same RNTI to multiple WTRUs, for example,if CB-PUSCH resources are available in the applicable cell(s). The WTRUmay derive the RNTI based on a WTRU-specific identity. For example, suchgrant may be for a transmission of data on a PUSCH resource dedicated tothe WTRU. For example, such grant may be for a transmission of data on ashared PUSCH resource, for example, using CB-PUSCH. For example, suchdata may be user plane data (e.g., for short downlink data transfersand/or (e)BSR, such as described herein). For example, such data mayconsist of control signaling (e.g., such as described herein). Forexample, if the WTRU is synchronized (e.g., according to any of theexamples described herein), the WTRU may transmit on a PUSCH resourceusing the grant information. The WTRU may determine how to transmit(e.g., resource, timing, etc.) on the PUSCH using legacy methods or fora subset of parameters using examples described herein.

HARQ A/N may be applicable for extended paging functionality, forexample, in case of WTRU-specific DCI. For examples described herein, ifthe WTRU is synchronized (e.g., according to any of the proceduresdescribed herein), the WTRU may transmit HARQ feedback on PUCCH. Forexample, such HARQ feedback may be transmitted for the reception of theDCI and/or for the reception of the associated PDSCH (e.g., if any). TheWTRU may determine how to transmit (e.g., resource, timing) on the PUCCHbased on the location of the received DCI on the PDCCH (e.g., based onthe identity of the first Control Channel Element of the DCI similar tolegacy methods) and/or using an offset determined from the receivedcontrol signaling. If the DCI includes a downlink assignment for adelayed PDSCH assignment (e.g., as described herein), the WTRU maydetermine the applicable resource on PUCCH using a similar examplesand/or using a timing based on the reception of the PDSCH.

RNTI decoding for extended paging functionality is contemplated. For theRNTI(s) that may be common to multiple WTRUs, a DCI may be received inthe common search space of the cell. When such RNTI is configured by thenetwork using dedicated signaling (e.g., the RNTI may be common tomultiple WTRUs in the cell), a DCI may be received in a search spacethat may be common to the group of WTRUs and/or might not be part of thecommon search space of the cell.

Paging to synchronized WTRUs and DL data transfer, such as short DL datatransfers or L3 (re)connection signaling (e.g., NW configures), iscontemplated. Such paging functionality may be utilized to reducelatency for downlink data arrival, for example, when user plane data maybe sent alongside the paging information (e.g., short data transfers).Such paging functionality may be utilized to reduce latency for(re-)establishment of an RRC connection when control plane data may besent alongside with the paging information (e.g., fast (re-) connectionestablishment). The PDSCH transmission may be received with some delay,such as the delayed PDSCH assignment may be valid for a PDSCHtransmission 4 ms after reception of paging. In particular, whencombined with the use of a WTRU-based synchronization channel asdescribed herein.

Paging to synchronized WTRUs and DL data transfer, such asDCI(DL)+PDSCH(RRC (re)connection), is contemplated. For example, thesynchronized WTRU (e.g., possibly using any of the examples describedherein) may determine from a (e.g., first) received DCI (e.g., and/orthe PDSCH) in subframe n that it is being paged by the network. It maydetermine from a (e.g., second) DCI in subframe n (e.g., or later) thatthere is a PDSCH transmission in a possibly later subframe e.g. n+4. TheWTRU may receive a L3 message that, for example, re-establishes,reconnect(s) or initiate the establishment of a RRC connection.

Paging to synchronized WTRUs and UL data transfer, such as NW-initiatedL3 (re)connection signaling (e.g., triggers WTRU request), iscontemplated. Such paging functionality may be utilized to reducelatency for (re-)establishment of an RRC connection. For example, asynchronized WTRU in RRC IDLE (e.g., or in RRC-Inactive) may receive apaging message together with a grant for an uplink transmissions, inwhich case the WTRU may initiate (e.g., immediately) initiate a RRCConnection Establishment or a connection re-establishment/reactivationprocedure (e.g., if supported). In particular, when combined with theuse of a WTRU-based synchronization channel as described herein.

Paging to synchronized WTRUs and UL data transfer, such asDCI(DL)+DCI(UL:CB-PUSCH(RRC (re)connection)), is contemplated. Forexample, the synchronized WTRU (e.g., using any of the examplesdescribed herein) may determine from a (e.g., first) received DCI (e.g.,and/or a PDSCH) in subframe n that it is being paged by the network, andit may determine from a (e.g., second) DCI in subframe n (e.g., orlater) that there may be a CB-PUSCH resource available in subframe e.g.n+4. The WTRU may then transmit a L3 message that, for example,re-establishes, reconnect(s) or requests the establishment of a RRCconnection.

Extensions to legacy paging, and/or additional paging function iscontemplated. For example, the WTRU may use such a paging mechanismeither as extensions to an existing paging functionality (e.g., asdescribed herein) or in parallel to a legacy paging mechanism (e.g., asdescribed herein).

Extended Paging Information and/or Control Signaling is contemplated.Extensions may include means to identify the WTRU and a context and/orgrant resources. For example, such extended paging information orcontrol signaling may include at least one of the following: anidentity; a grant for uplink transmission; and/or a CB-PUSCH trigger. Anidentity may be WTRU-specific, either in the cell or in an area. Anidentity may be used in conjunction with another identity thatidentifies the WTRU (e.g., such as the identity in the legacy pagingmessage). An identity may be associated with a L3 context. For example,the identity may corresponds to a L3 context previously configuredand/or used by the WTRU. The identity may have been part of the WTRU'sconfiguration of the L3 context. The context may include an RRCConnection, a security context, a bearer configuration or any otheraspect of the WTRU's configuration. One or more configuration aspectsmay also be included in the context. For example, the WTRU may determinethat an RRC connection may be reactivated following reception of suchcontrol signaling. For example, the WTRU may perform such behavior whensuch signaling may be received when the WTRU is in RRC IDLE mode or inRRC-Inactive mode. A grant for uplink transmission may be received in aDCI similar to the legacy grant information or on PDSCH, for example,similar to a grant received in the legacy RAR. A CB-PUSCH trigger maycomprise the WTRU receiving an indication to initiate a transmission onCB-PUSCH.

An extended paging may trigger L3 (re-)connection procedure, with noRACH needed. The WTRU may initiate a L3 procedure that (re-)establishesor reactivates an RRC connection upon reception of such controlsignaling. If the received control signaling includes a grant for anuplink transmission, the WTRU may transmit the connection request usingthe received grant. For example, the response to the received controlinformation (e.g., a connection request) may include the receivedidentity. For example, the response may include a unique transactionidentifier. Such identifier may be generated by ciphering and/orperforming integrity protection of the received identity using thesecurity context associated with the received identifier and maysubsequently be used to validate the L3 procedure. Additional validationmay be based on successful authentication and/or deciphering of asubsequent L3 message received from the network (e.g., a connectionreconfiguration). This may be useful in case L3 context identities maycollide in the paging functionality.

Extended paging information and control signaling may be applicable toCONNECTED but inactive/synchronized WTRUs. In one example, the WTRU mayreceive such control information when in RRC CONNECTED (e.g., or inRRC-Inactive) mode. In such case, the WTRU may transmit user plane data(e.g., immediately) using the received grant.

Paging extensions is contemplated. In one example, such paging mechanismmay be based on the legacy paging functionality with the addition of anumber of extensions. [Monitoring of legacy paging channel+additionaloccasions]

Monitoring of legacy paging channel and additional occasions forextended paging is contemplated. For example, the paging occasions thatmay be specific to the extending mechanism may be a subset of thetypical (e.g., legacy) paging occasions (e.g., low frequency). Forexample, the set of legacy paging occasions may be augmented such thatthe WTRU may use additional paging occasions. For example, the pagingoccasions that are specific to the extended mechanism may use a periodthat corresponds to a fraction of the period used for the typical (e.g.,legacy) paging occasions (e.g., high frequency so latency gain is afixed ratio of the IDLE mode latency). In this case, some or all of thelegacy paging occasions may overlap with an occasion for the extendedmechanism (e.g., for alignment for better WTRU power savings).

Signaling inside paging channel and backward compatible extensions forextended paging is contemplated. For example, the paging informationreceived using the legacy paging function may include at least one ofthe type of information described herein.

Parallel paging function is contemplated. In one example, such pagingmechanism may be configured to operate in parallel with legacyfunctionality, such as legacy paging (e.g., in idle mode or ininactivity mode) or such as PDCCH monitoring (e.g., including DRX whenin connected mode, or in inactivity mode).

Monitoring of parallel paging channel is contemplated. For example, theWTRU may determine specific paging occasions. For example, a similarfunction may be used to derive a set of occasions that are mutuallyexclusive to the legacy paging occasions (e.g., any frequency may bepossible). For example, the set of legacy paging occasions may beaugmented such that the WTRU may use additional paging occasions. Forexample, the paging occasions that are specific to the extendedmechanism may correspond to a subset of the (e.g., legacy) pagingoccasions (e.g., low frequency). For example, the paging occasions thatare specific to the extended mechanism may use a period that correspondsto a fraction of the period used for the (e.g., legacy) paging occasions(e.g., high frequency so latency gain may be a fixed ratio of the IDLEmode latency). In this case, some or all of the legacy paging occasionsmay overlap with an occasion for the extended mechanism (e.g., foralignment for better UE power savings).

Signaling inside paging channel for parallel paging function iscontemplated. For example, the paging information received using theparallel paging function may include at least one of the type ofinformation described herein.

WTRU-autonomous uplink timing synchronization is contemplated. A WTRUmay autonomously maintain valid uplink synchronization at low cost tothe WTRU and/or to the network without being managed by the scheduler(e.g., independent from the connectivity state of the WTRU). Theimmediate uplink transmissions in any RRC mode may be enabled, forexample, to circumvent the need for the random access procedure.

The WTRU may use a channel that is akin to a subset of the functionalityof the PRACH. When synchronized, the WTRU may use a signal that is akinto a SRS transmission. The WTRU may autonomously remain in asynchronized state, for example, possibly without requesting uplinkresources, possibly without performing a transmission on a dedicatedresource, and possibly without being actively managed by the scheduler(e.g., for WTRUs in RRC Connected mode but inactive) and/or withoutbeing known to the network (e.g., for WTRU's in RRC IDLE mode). Theexamples for WTRU-autonomous uplink timing synchronization may beapplicable to WTRU-autonomous mobility (e.g., if such is supported inRRC Connected mode or in Inactive mode) and to IDLE mode mobility. TheWTRU-autonomous uplink timing synchronization may enable quicker accessto a PUSCH transmission, such as CB-PUSCH. For example, the examples maywork well in combination with CB-PUSCH (e.g., dynamically granted ornot) and pre-allocation mechanism (e.g., similar to SPS). The resourcesused may have a smaller overhead. For example, the method forWTRU-autonomous uplink timing synchronization may be based on a sharedchannel. Possibly, the method may make use of a shared channel forinitially gaining uplink synchronization and use a dedicatedresource/channel otherwise.

The RSSC resources for WTRU-autonomous uplink timing synchronization maybe distinct (e.g., preamble, PRB or time) from PRACH. The RSSC resourcesmay be distinct from DSS resources (e.g., type, time). The WTRU may beconfigured with resources for performing the uplink transmissionsnecessary for the WTRU-autonomous uplink synchronization procedure.Different types of signals may have different resource configuration,such as in time and frequency. For example, the RSSC may be configuredwith specific resources in terms of time (e.g., RSSC transmissionoccasions), frequency (e.g., in terms of starting PRB) and length (e.g.,in terms of number of PRBs for the signal, such a six PRBs may be used).For example, for a DSS signal that may be similar to a sounding signal(e.g., SRS), resources similar to the legacy SRS may be configured forthe WTRU, including periodic transmission occasions.

Procedural aspects for WTRU-Autonomous Synchronization are contemplated.A WTRU may acquire and maintain DL timing synchronization. The WTRU mayacquire and maintain downlink synchronization to a cell. Such downlinktiming synchronization may be based on downlink reference signals. Suchsignals may include PSS, SSS or CRS. For example, the WTRU in RRCCONNECTED mode (e.g., or in RRC-Inactive mode) may be configured withsuch a cell as a serving cell. For example, the WTRU in RRC IDLE mode(e.g., or in RRC-Inactive mode) may be camping on such a cell.

The WTRU may be configured with a synchronizationchannel/signal/procedure. The WTRU may receive (e.g., either frombroadcast signaling, or from dedicated signaling) a configuration forthe WTRU-autonomous synchronization procedure.

The WTRU may determine to use a synchronization procedure, for example,when in CONNECTED mode. For example, the WTRU in RRC CONNECTED mode(e.g., or in RRC-Inactive mode) may receive dedicated signaling to thiseffect. The WTRU may receive dedicated signaling (e.g., L2/MAC CE, orL3/RRC) that may indicate that the WTRU may use the procedure for thepurpose of maintaining uplink timing synchronization.

The WTRU may determine to use a synchronization procedure, for example,when in IDLE mode. For example, the WTRU in RRC IDLE mode (e.g., or inRRC-Inactive mode) may receive broadcasted signaling to this effect. TheWTRU may determine to use such synchronization procedure based on RRCstate and/or based on whether or not it may determine that the cellsupports such procedure and related transmissions.

A configuration may comprise, for example, TAT, prohibit, Maxretransmissions or timer. The WTRU may be configured with an initialvalue for the Timing Alignment Timer (TAT_(UE) _(_) _(SYNC)) associatedwith the synchronization procedure. This value may be equivalent to thevalue of the TAT (e.g., if TAT is configured and/or available). TAT_(UE)_(_) _(SYNC) may be referred to as TAT. The WTRU may be configured witha maximum period for updating the UL timing alignment. The period may bea fraction of the value of the TAT. The WTRU may be configured with aprohibit timer and/or with a retransmission timer and/or with a maximumnumber of attempts for a given WTRU-autonomously initiatedsynchronization procedure, some or all of which may be applicable totransmission of uplink synchronization requests.

Triggers for WTRU-autonomous uplink transmission request/WTRU-autonomousuplink synchronization are contemplated. The WTRU may determine toperform a WTRU-autonomous uplink synchronization based on detecting oneor more triggers. For example, the WTRU may transmit an uplinktransmission request and/or perform autonomous UL timingadjustment/synchronization based on one or more of the WTRU TAT status,occurrence of mobility event and/or change of cell, reception ofdownlink signaling by the WTRU (e.g. RSSC trigger or aperiodic trigger),data being available for transmission (e.g., SR overload), the DL timingreference (e.g., a change in the DL timing reference), and/or DLpathloss measurements (e.g., a change in the pathloss measurements).

The TAT status may be used as a trigger for the WTRU to performautonomous UL timing adjustment and/or to perform an uplink transmissionrequest. For example, the WTRU may perform autonomous UL timingadjustment and/or may perform an uplink transmission request based ondetermining that the TAT is about to expire. For example, the WTRU mayperform autonomous UL timing adjustment and/or may perform an uplinktransmission request upon determining that less than a certain amount ornumber of WTRU-autonomous timing occasions are remaining/available untilthe expiration of the TAT (e.g., the number of remaining occasions maybe 1, 2, etc.).

Occurrence of a mobility event and/or change of cell may be used as atrigger for the WTRU to perform autonomous UL timing adjustment and/orto perform an uplink transmission request. For example, the WTRU mayperform autonomous UL timing adjustment and/or may perform an uplinktransmission request based on determining that it has changed cell. Suchchange of cell may be due to a network-controlled handover (e.g., inCONNECTED, Inactive mode), a WTRU-autonomous cell reselection (e.g. inIDLE, Inactive mode), and/or WTRU-autonomous forward mobility (e.g., ifsupported in CONNECTED mode). For example, certain mobility eventsand/or certain types of cell changes may trigger the WTRU to performautonomous UL timing adjustment and/or an uplink transmission request,while other types might not trigger the autonomous UL timing adjustmentand/or uplink transmission request.

Reception of downlink signaling (e.g., RSSC trigger or aperiodictrigger) may be used as a trigger for the WTRU to perform autonomous ULtiming adjustment and/or to perform an uplink transmission request. Forexample, the WTRU may be configured to decode a DCI on PDCCH using aspecific RNTI (e.g., either WTRU-specific, group-specific orcell-specific). Such DCI may indicate that resources for uplinktransmission request and/or UL timing alignment are available to theWTRU.

Data being available for transmission (e.g., SR overload) may be used asa trigger for the WTRU to perform autonomous UL timing adjustment and/orto perform an uplink transmission request. For example, the WTRU maydetermine that uplink data has become available for transmission and mayperform autonomous UL timing adjustment and/or may perform an uplinktransmission request based on determining the data is available fortransmission. For example, a trigger for performing autonomous UL timingadjustment and/or performing an uplink transmission request maycorrespond to data of a specific bearer becoming available fortransmission (e.g., other bearers might not trigger the request). Atrigger for performing autonomous UL timing adjustment and/or performingan uplink transmission request may correspond to an amount of data thathas specific QoS requirements becoming available for transmission. Atrigger for performing autonomous UL timing adjustment and/or performingan uplink transmission request may correspond to the amount of databeing available for transmission being relative to (e.g., below) acertain threshold. The triggers based on data becoming available fortransmission (e.g. amount of data, identity of the bearers, thethreshold based triggers, etc.) may be configuration aspects of the WTRUand may be received as configured parameters. For example, theoccurrence of data being available for transmission may be a trigger forthe WTRU to perform autonomous UL timing adjustment and/or to perform anuplink transmission request when the WTRU is unsynchronized, but notwhen the WTRU is synchronized. For example, the WTRU may performautonomous UL timing adjustment and/or perform an uplink transmissionrequest when it is also requesting uplink transmission resources, (e.g.,such as SR and/or CB-SR), but not when it is not requesting uplinktransmission resources.

Information related to and/or changes in the DL timing reference may beused as a trigger for the WTRU to perform autonomous UL timingadjustment and/or to perform an uplink transmission request. Forexample, the WTRU may determine that a change in the downlinksynchronization has occurred and may perform autonomous UL timingadjustment and/or may perform an uplink transmission request based ondetermining that a change in the downlink synchronization has occurred.For example, the WTRU may determine that a change in DL timing hasoccurred based on downlink synchronization signal(s). Examples ofdownlink synchronization signals that may be used to determine if achange in DL timing has occurred may include one or more of a PrimarySynchronization Signal (PSS) and/or a Secondary Synchronization Signal(SSS). The determination that a change in DL timing has occurred may bebased on reception of best/strongest path for the synchronizationsignals. For example, the signals used to determine if a change in DLtiming has occurred may be other type of reference signals such asCell-specific Reference Signals (CRS) or other signals that servesimilar purposes. The WTRU may determine that a change in DL timing hasoccurred due to an autonomous update of the value of N_(TA). Forexample, WTRU may determine that a change in DL timing has occurred whenthe WTRU performs an autonomous update of the value of N_(TA) thatexceeds a certain threshold. For example, if the updated value forN_(TA) exceeds the value of N_(TA) at the time the WTRU last received aTAC from the eNB by a certain threshold, the WTRU may determine that achange in DL timing has occurred. For example, if the cumulative updatesto the value of N_(TA) since the WTRU last received a TAC from the eNBexceeds a certain threshold the WTRU may determine that a change in DLtiming has occurred.

DL Pathloss measurements (and/or change in received power levels) may beused as a trigger for the WTRU to perform autonomous UL timingadjustment and/or to perform an uplink transmission request. The WTRUmay perform pathloss measurements and/or estimation of pathloss. TheWTRU may determine that a change in downlink pathloss has occurred andthe WTRU may perform autonomous UL timing adjustment and/or may performan uplink transmission request based on determining that the change indownlink pathloss has occurred. For example, if a change in pathlossestimation exceeds a certain threshold the WTRU may perform autonomousUL timing adjustment and/or may perform an uplink transmission request.For example, if a pathloss estimation exceeds the pathloss estimated atthe time the WTRU last received a TAC from the eNB by a certainthreshold, the WTRU may perform autonomous UL timing adjustment and/ormay perform an uplink transmission request. For example, if thecumulative changes in pathloss estimation since the WTRU last received aTAC from the eNB exceeds a certain threshold, the WTRU may performautonomous UL timing adjustment and/or may perform an uplinktransmission request. Using pathloss as a trigger performing autonomousUL timing adjustment and/or performing an uplink transmission requestmay be particularly applicable for TDD systems and/or for cells withhigh level of channel reciprocity between the downlink and the uplink,although such techniques may also be used in FDD systems. Using pathlossas a trigger, autonomous UL timing adjustment and/or uplink transmissionrequests may be used in combination with a determination of a change inDL timing. For example, the WTRU may initiate the uplink synchronizationprocedure to perform autonomous UL timing adjustment and/or perform anuplink transmission request based on the occurrence of both a change inpathloss and a change in DL timing. For example, the trigger may bebased on the occurrence of either a change in pathloss or a change in DLtiming (e.g., when one or more criteria would be met for the same, ordifferent, serving cells).

Transmission of uplink transmission request is contemplated. When theWTRU determines that it may transmit an uplink timing synchronizationrequest, the WTRU may perform at least one of the following: the WTRUmay count the number of transmissions of uplink transmission request;the WTRU may transmit the uplink synchronization transmission request;and/or the WTRU may start a supervisory timer for theprocedure/retransmission. When the WTRU may count the number oftransmissions of uplink transmission request, the WTRU may increment itstransmission count. If the WTRU determines that the count exceeds themaximum number of attempts, the WTRU may determine that thesynchronization update procedure was not successful. If no transmissioncount is used, then it may be equivalent to setting the value to 1. Whenthe WTRU may transmit the uplink synchronization transmission request,the WTRU may perform a transmission of an uplink synchronizationrequest, for example, using either the RSSC or the DSS as describedherein. When the WTRU may start a supervisory timer for theprocedure/retransmission, the WTRU may start a retransmission timer, andif the WTRU determines that the retransmission timer has expired, theWTRU may determine that it shall transmit another uplink timingsynchronization request at the next occasion. If no retransmission isused for the synchronization update procedure, it may be equivalent tosetting the value of the timer to infinity.

If the WTRU autonomously determines that it may perform a transmission,it may perform the above in the subframe that correspond to the nexttransmission occasion for the channel. Otherwise, the WTRU may use thefirst occasion that occurs no later than a specific period (e.g., x ms)after the reception of the control signaling (e.g., NW-ordered) thattriggered such transmission or after the expiration of a timer, such asTAT.

The WTRU may determine when to receive the response. For example, theWTRU may determine that the response to the request may be expected inone of a set of one or more (e.g., consecutive) subframe(s). Forexample, in case the response is synchronized with the occasion for theuplink transmission of the request in subframe n, the WTRU may determinethat the set consist of exactly one subframe, for example, subframe n+xwhere x may correspond to a processing time e.g. x=4. For example, incase the response is not synchronized to such granularity, the WTRU maydetermine that the set consist of a plurality of subframes, such assubframes [n+x, n+y] where x may correspond to a processing time e.g.x=4 and where y may correspond to the length of a reception window. TheWTRU may determine that it has not successfully received a response ifit cannot successfully decode such response in any such subframe(s).

When the WTRU successfully receives a response from the network to theuplink timing synchronization request, the WTRU may perform at least oneof the following: the WTRU may start (e.g., or restart) the applicableTAT; or, the WTRU may set the initial transmission power to the valueused by the last performed transmission of the uplink timingsynchronization request.

When the WTRU determines that it has failed to receive a response forthe transmitted uplink timing synchronization request, the WTRU mayperform at least one of the following: the WTRU may perform a randombackoff, for example, if retransmissions are not applicable to thesynchronization update procedure; or the WTRU may start a prohibittimer, for example, if retransmissions are not applicable to thesynchronization update procedure.

When the WTRU determines that it has failed to complete thesynchronization procedure (e.g., the WTRU fails to access uplink timingsynchronization channel and/or to get a response for the transmission ofa request), the WTRU may perform at least one of the following: the WTRUmay retry later; the WTRU may perform a legacy access procedure; theWTRU may change RRC state in case such procedure is necessary to thestate; and/or the WTRU may invalidate the configuration for thesynchronization procedure. If the WTRU derides to retry later, the WTRUmay start a prohibit timer. The WTRU might not initiate a transmissionof a synchronization update request while the timer is running. If theWTRU performs a legacy access procedure, the WTRU may perform the legacyprocedure for accessing resources of the cell. For example, this may beapplicable if the procedure is triggered due to reception of paging,such as described herein, for example, for DL data arrival and/or forRRC connectivity. For example, this may be applicable if the procedureis triggered due to data becoming available for transmission in the WTRUand if the request is used for requesting uplink resources fortransmission. If the WTRU changes the RRC state in case such procedureis necessary to the state, the WTRU may transit to RRC IDLE, forexample, if the WTRU performs this transition from the RRC-Inactivestate. The WTRU may first initiate the transmission of a L3 notificationto the network, for example, if the WTRU performs this transition fromthe RRC CONNECTED state. If the WTRU invalidates the configuration forthe synchronization procedure, the WTRU may invalidate the configurationof the channel (e.g., SSRC) or the configuration for the signal (e.g.,DSS) used for transmission of the uplink synchronization request. TheWTRU may invalidate the configuration of the procedure itself (e.g.,including both RSSC and DSS, if configured), for example, for aconfiguration that was received by dedicated signaling and/or for aconfiguration that is dedicated to the WTRU.

A Random Shared Synchronization Channel (RSSC) is contemplated. Forexample, a WTRU may obtain and/or maintain uplink synchronization usinga physical uplink channel designed for this purpose, among otherscenarios. A transmission using such a channel may include data (e.g.control plane data and/or user plane data).

The channel used for autonomously obtaining and/or maintaining uplinksynchronization may be referred to as the RSSC. For example, the RSSCmay be a PRACH-like channel. The RSSC may use a waveform with certainspectral containment properties (e.g. for CB-PUSCH), for example awaveform that has better spectral containment than legacy LTE waveforms(e.g., SC-FDMA). Transmissions on the RSSC might not be performed evenwhen the WTRU might lack tight uplink synchronization. For example,transmissions on the RSSC may include a cyclic prefix and/or a guardband to protect against interference from transmissions from other WTRUson adjacent subcarriers and/or in adjacent TTIs. Transmissions on theRSSC may use a different (e.g., a second) transmission method (and/ormode, type, etc.) than a (e.g., first) transmission method that may beutilized when the WTRU has uplink synchronization. For example, thesecond transmission method may be a non-orthogonal uplink transmission.For example, the transmissions on the RSSC may be based on a differentwaveform, such as a filtered OFDM waveform. For example, the waveformutilized for transmission on the RSSC may be characterized by relativelyhigh spectral containment that may facilitate reception at the receiver,perhaps for example even when the transmission is performed with lessstringent synchronization at the transmitter compared to thesynchronization requirements when transmission are performed using afirst method that uses a cyclic-prefix based OFDM transmission. Suchtransmission techniques may be performed according to principles of the5gFLEX system described herein, or the like. Transmissions by the WTRUon the RSSC may include data (e.g., control plane and/or user planeinformation). For example, transmissions on the RSSC may be used forcontention-based access channel. For example, RSSC resources may beallocated to the WTRU using dynamic signaling on PDCCH and/or bysemi-static provisioning (e.g., RRC signaling). The RSSC resources maybe located in the PUSCH region of the uplink carrier (e.g., CB-PUSCH)and/or in a region dedicated for transmission of RSSC signals (e.g., inco-existence with legacy LTE transmissions). The RSSC resources may bepre-allocated to the WTRU using semi-persistent configuration, and/orthe like.

The RSSC may be used for obtaining and/or for maintaining uplinksynchronization for WTRUs that might not be actively being scheduled.For example, the RSSC may be used for maintaining uplink synchronizationfor WTRUs that have not been scheduled using dedicated signaling. Insuch scenarios, among others, the WTRU may autonomously initiate atransmission on such a channel. For example, the RSSC may be used by aWTRU, perhaps without receiving an explicit allocation of resources. Thenetwork may be unaware of the identity of the WTRU that is utilizing theRSSC and/or transmitting on such a channel, and/or may continue to beunaware of the identity of the WTRU during the RSSC use. In one or moretechniques, WTRU-specific demodulation reference signals may be used toindicate the identity of the transmitting WTRU.

The WTRU may use the RSSC prior to and/or as a prelude to the use ofCB-RNTI grants. For example, the RSSC may be available to WTRUs in IDLEmode and/or may be available to WTRUs in RRC CONNECTED mode in long DRX.A transmission on the RSSC may be a way for the WTRU to signal a requestfor a CB-PUSCH resource. A request for a CB-PUSCH resource may bereferred to as a CB-SR. For example, a transmission on the RSSC mayinclude an indication of a size of a request CB-PUSCH and/or PUSCHresource (e.g., minimum guaranteed size or specific size, etc.). Aresponse to a WTRU transmission on the RSSC may include one or more of aTAC, a transmit power control (TPC) and/or parameters for CB-PUSCHaccess, such as CB-RNTI for PDCCH decoding.

For example, the WTRU may obtain and/or maintain uplink synchronizationusing a physical uplink channel designed for the synchronization updateprocedure.

Synchronization may be possible without pro-active actions from thescheduler. Such channel might not utilize the allocation of dedicatedresources. Such a channel might not require knowledge of the identity ofthe WTRU by the network. The WTRU may use this channel as a prelude toother types of uplink transmissions using resources requiring uplinktiming alignment. Such channel may be accessible to WTRUs in IDLE modeand to WTRUs in RRC CONNECTED mode, including WTRUs in long DRX.

Transmissions on RSSC may share similar principles as PRACHtransmissions. The RSSC may be similar in structure and in configurationto the legacy PRACH channel. The RSSC may be configured such that thenetwork may distinguish between PRACH and RSSC. The RSSC and PRACH maybe distinct channels from a WTRU and a system perspective.

A second/different waveform may be used to directly access CB-PUSCHresources. For example, the RSSC may be a contention-based channel forPUSCH-like transmissions, e.g., similar to the CB-PUSCH channel, but mayutilize a second transmission method and/or different waveform. Forexample, wherein used herein the term a second transmission method mayrefer to a transmission method that uses a different waveform than afirst transmission method (e.g., a waveform that is different than thewaveform used in legacy LTE systems such as SC-FDMA). For example, thesecond transmission method may use a filtered-type of OFDM waveform(e.g., Filtered Bank Multi Carrier OFDM-FBMC-OFDM and/or UniversalFiltered OFDM-UF-OFDM, etc.).

Signaling aspects, such as uplink timing synchronization request, arecontemplated. For example, the signal transmitted on RSSC may be similarto a preamble on PRACH. For example, a transmission format for RSSC maybe characterized by at least one of the following: CP/guard size (e.g.,the signal may include protection for timing misalignment); preamblelength (e.g., the signal may be transmitted over one or multiplesubframes); number of PRBs (e.g., the signal may be transmitted over oneor multiple PRBs); and/or transmission method (e.g., the signal may betransmitted using a different transmission mode/waveform).

A transmission format for RSSC may be characterized by a signalincluding protection for timing misalignment. For example, atransmission format for RSSC may be characterized by a CP/guard size.The transmission of a signal on the RSSC may include a guard in time(e.g., a CP/guard size). A reduced/limited maximum cell size may enablesmaller cyclic prefix/guard. For example, a transmission format for RSSCmay include a prefix/guard of 0.05 ms, e.g., for cells up to 7.46 km inradius.

A transmission format for RSSC may be characterized by transmitting asignal over one and/or multiple subframes. For example, a transmissionformat for RSSC may be characterized by a preamble length. If the signalis transmitted over one or multiple subframes, the signal transmitted onthe RSSC may be similar to a preamble used on PRACH, such as preamblelength. Reduced/limited maximum cell size may allow for a smaller numberof prefixes and/or eases preamble power detection at the receiver. Thismay enable shorter preambles, such as 0.4 ms. For example, if a subsetof access attempts utilized low latency (e.g., new WTRU rules may beimplemented to enforce this), fewer WTRUs may concurrently access suchresource than for a normal PRACH resource. A preamble format four may beused for TDD. The preamble format 4 may have a sequence length of 0.1 msfor UpPTS. Shorter preambles with higher initial power may be used.

A transmission format for RSSC may be characterized by transmitting asignal over one or multiple PRBs. For example, a transmission format forRSSC may be characterized by a number of PRBs. When the signal may betransmitted over one or multiple PRBs, the signal transmitted on theRSSC may be similar to a preamble used on PRACH such that 6 PRBs may beused (e.g., number of PRBs). Fewer than 6 PRBs may be used, for example,if enabled by the use of shorter preambles and better preamble detectionat the receiver.

A transmission format for RSSC may be characterized by transmitting asignal using a different transmission mode/waveform. For example, atransmission format for RSSC may be characterized by a transmissionmethod. The signal using a different transmission mode/waveform, and/orthe transmission used to obtain uplink synchronization, may betransmitted as described herein. For example, such transmission may be anon-orthogonal transmission. The WTRU for example may access a CB-PUSCHresource by performing a transmission using a second transmission methodbased on a different waveform, such as, e.g., a filtered OFDM waveform(e.g., Filtered Bank Multi Carrier OFDM-FB-OFDM, and/or UniversalFiltered OFDM-UF-OFDM, etc.). The transmission using the secondtransmission method based on a different waveform may include data (e.g.control plane data and/or user plane data). The WTRU may subsequentlyreceive a TAC and resume transmissions according to the firsttransmission method (e.g. legacy cyclic-prefix based LTE transmissionsor similar).

The resources used may be dynamically scheduled to control overhead.RSSC occasions and/or resources may be semi-statically configured, forexample, in SIB. RSSC occasions and/or resources may be dynamicallyscheduled, for example, using a RNTI. Such RNTI may be common for asubset of, or all, WTRUs in a cell and one or more (e.g., each) WTRU maybe configured with a specific frequency offset and/or signature (e.g., apreamble). The RSSC occasion may be common to multiple WTRUs and theresource (e.g., in terms of PRB(s), or in terms of signature, such as apreamble) utilized may be dedicated per WTRU. Such RNTI may be dedicatedfor each WTRU. Signaling similar to PDCCH order may be used to enablethe uplink transmission from the WTRU. The WTRU may autonomouslydetermine whether or not it may perform an uplink synchronizationrequest using a RSSC transmission. RSSC occasions and/or resources maybe associated to a specific SOM (e.g. including scheduling of concernedresources using a downlink control channel associated with theapplicable SOM).

The RSSC may be available independently of the synchronization stateand/or scheduling. For example, the WTRU may access this channel and/orresource independently of whether it is in synchronized state or not.The WTRU may be configured to use the RSSC for uplink synchronization.The RSSC may be used in conjunction with normal legacy uplink timingalignment functionality, for example, for a WTRU that is being activelyscheduled by the network and/or for a WTRU in RRC CONNECTED mode.

An RSSC may be available for an unsynchronized state (e.g., an RSCC maybe unavailable for a synchronized state). For example, the WTRU mayaccess this channel and/or resource when it is in unsynchronized state.For example, the WTRU may use the RSSC when the TAT_(RSSC) is notrunning (e.g., not when the TAT_(RSSC) is running). The WTRU may use adifferent signal, such as described herein, when it is in synchronizedstate (e.g., when the TAT_(RSSC) is running).

In one or more techniques, the WTRU may access this channel and/orresource perhaps for example when (e.g., only when) it might not havevalid uplink synchronization and/or perhaps when (e.g., only when) theWTRU may have data available for transmission in the uplink (e.g. usinga second transmission method such as described herein). Such data mayinclude a buffer status report (BSR). For example, a WTRU in CONNECTEDmode may transmit a BSR (e.g., perhaps only a BSR) on such s channel inwhich perhaps the procedure may be triggered by new data and/or data ofhigher priority than data already in the WTRU's buffer becomingavailable for transmission. For example, a WTRU in IDLE mode maytransmit L3/RRC signaling to establishing a new (e.g., fresh) RRCconnection, and/or or re-establishing and/or reconnecting a previouslyexisting RRC connection (e.g., perhaps with a BSR—for example perhaps ifthere is further data available for transmission).

The RSSC may be available when no Dedicated Synchronization Signal (DSS)is configured and/or valid (e.g., RSSC not available when DSS isconfigured and/or valid). For example, the WTRU may access this channeland/or resource perhaps for example if it determines that it does nothave a valid configuration for DSS and/or for example not when itdetermines that is has a valid DSS configuration. The WTRU may use theRSSC, for example, other means to send a request for uplinksynchronization are unavailable. If the WTRU has a valid DSSconfiguration, the WTRU may use DSS, such as described herein perhapsfor example when it is in synchronized state (e.g., when the TAT_(RSSC)is running and/or perhaps if the WTRU might not have data available fortransmission).

The WTRUs might not be known to the network to maintain synchronization.Such synchronization channel may be available to any WTRU in a cell,such as actively scheduled WTRUs, inactive WTRUs, and/or WTRUs in IDLEmode.

This channel may also be used to signal that a CB-PUSCH resource may beneeded (some form of CB-SR). In such case, the response from the networkmay include a TAC, power control information (e.g. TPC), a CB-RNTIand/or a grant for an uplink transmission. In other words, atransmission on the RSSC may (re-)activate scheduling CB-PUSCH in acell. The UE may trigger CB-SR when data becomes available for aspecific bearer and/or when the amount of data has specific QoSrequirements and/or if the amount of data is below a certain threshold,each of which may be configuration aspects of the WTRU.

The use of a second/different waveform to access CB-PUSCH resources iscontemplated. In one or more techniques, such a channel may be acontention-based channel for PUSCH-like transmissions similar to theCB-PUSCH channel. The channel may use a second/different transmissionmethod, for example for the purpose of at least one of: performing adata transmission, obtaining uplink synchronization (e.g. in a downlinktransmission containing a TAC), and/or for performing furthertransmission of data using a first waveform, perhaps for example usingan update uplink timing advance determined from a TAC received from thenetwork.

The Dedicated Synchronization Signal (DSS) is contemplated. For example,a WTRU may obtain and/or maintain uplink synchronization using thetransmission of a signal on an uplink resource designed for thispurpose.

The DSS may be used for maintaining uplink synchronization for WTRUsthat might not be actively being scheduled. Such resource may utilizethe allocation of resources dedicated to such procedure. The resourcesmight not utilize knowledge of the identity of the WTRU by the network.Such resource may be assigned to a single WTRU. The WTRU may use atransmission on such resource, for example, as a prelude to the use ofCB-RNTI grants.

For example, such resource may be available to WTRUs in IDLE mode and toWTRUs in RRC CONNECTED mode in long DRX. A transmission on this resourcemay be a way to signal that a CB-PUSCH resource may be needed (e.g.,CB-SR). The response received from the network may include a TAC, a TPCand/or parameters for CB-PUSCH access, such as CB-RNTI for PDCCHdecoding.

For example, the WTRU may obtain and/or maintain uplink synchronizationusing the transmission of a signal on an uplink resource for thesynchronization update procedure.

Synchronization may occur without pro-active actions from the scheduler.The DSS may utilize the allocation of dedicated resources (e.g., suchthat the network may ensure that no collision occur on this resource).The DSS might not utilize knowledge of the identity of the WTRU by thenetwork. The WTRU may use this resource as a prelude to other types ofuplink transmissions using resources requiring uplink timing alignment.Such resource may be accessible to WTRUs in IDLE mode and to WTRUs inRRC CONNECTED mode, including WTRUs in long DRX.

Transmissions on DSS may share similar principles as SRS transmissions.The DSS may be similar in signaling and in configuration to the legacySRS transmission. For example, the WTRU may obtain and/or maintainuplink synchronization using a physical uplink transmission designed forthe synchronization update procedure. A WTRU may perform suchtransmission in a synchronized state (e.g., not in the unsynchronizedstate).

The DSS resources used may be dynamically scheduled to control overhead.DSS occasions and/or resources may be semi-statically configured, forexample, by dedicated signaling. DSS occasions and/or resources may bedynamically scheduled, for example, using an RNTI. Such RNTI may becommon for a subset of, or all, WTRUs in a cell, and one or more (e.g.,each) WTRU may be configured with a specific frequency offset and/orsignature/sequence for signal generation. For example, the DSS occasionmay be common to multiple WTRUs and the resource used may be dedicatedper WTRU. Such RNTI may be dedicated for one or more (e.g., each) WTRU.Signaling similar to aperiodic SRS request may be used to enable theuplink transmission from the WTRU. The WTRU may autonomously determinewhether or not it may perform an uplink synchronization request using aDSS transmission.

Signaling aspects, such as downlink timing synchronization response, arecontemplated. The WTRU may receive a response on PDCCH and/or on PDSCH.For example, the WTRU may receive a response from the network followingthe transmission of the uplink timing synchronization request. Suchrequest may be a transmission on RSSC, such as described herein, or asignal on DSS, such as described herein. For example, such a responsemay include a DCI, perhaps received on the PDCCH. For example, the RSSCmay use a preamble-like transmission. The WTRU may decode such DCI onPDCCH using, for example, an RNTI that may be calculated as a functionof the uplink resource used for the transmission of the request (e.g.,using a similar calculation as for RA-RNTI in the random accessprocedure). This may apply for example, perhaps if the WTRU might notinclude any data in the request e.g. such as if a preamble, a DSS,and/or similar was used.

RSSC using a second type of transmission, for example with data and withDM-RS is contemplated. Such decoding may be performed using, forexample, a RNTI calculated as a function of a DM-RS (e.g. a resource,and/or a pattern thereof) used for the transmission of the request. Thismay apply in scenarios, perhaps for example including if the WTRUincluded data in the request (e.g. such as if a second type oftransmission, or the like, was used).

RSSC using a second type of transmission, for example with data, iscontemplated. For example, the identity of the WTRU may be based on theDM-RS and/or uplink resource that may be used.

Such decoding may be performed using, for example, a configured RNTI forthe WTRU (e.g. a C-RNTI perhaps for example if the transmission of therequest included capability for the network to determine the identity ofthe WTRU). For example, the WTRU may be configured to use aWTRU-specific DM-RS and/or the WTRU may use an assigned resource for thetransmission. Such resource(s) may be dedicated and/or shared (e.g. asemi-persistent grant which may be used by the WTRU, perhaps if the WTRUhas data to transmit). In scenarios including shared resource(s), theWTRU may be configured to use the WTRU-specific DM-RS in suchresource(s). This may apply perhaps for example, if the WTRU includeddata in the request (e.g. such as if a second type of transmission, orthe like, was used).

RSSC using a second type of transmission (e.g. with data) iscontemplated. The RNTI may be calculated, perhaps for example, based onthe resource(s) (e.g. in time and/or frequency used for the uplinktransmission).

Such decoding may be performed using, for example, a RNTI that may becalculated as a function of the uplink resource used for thetransmission of the request (e.g. in case of a transmission on PUSCH).Such RNTI may be used to decode a DCI using a similar technique as forRA-RNTI, for example. This may apply, perhaps for example if the WTRUincluded data in the request, such as if a second type of transmissionand/or the like, was used on a contention-based channel which may befollowed by the reception of a RAR on PDSCH, using such a RNTI value asthe RA-RNTI.

The DCI may comprise the TAC and/or TPC. For example, such DCI maycomprise at least one of a TAC, power control information (e.g., TPC).Such DCI may comprise a CB-RNTI allocation and/or a grant for an uplinktransmission (e.g., a dedicated grant or a contention-based grantdepending on whether or not (e.g., respectively) the request that may beused a dedicated resource and/or included capability for the network todetermine the identity of the WTRU). The DCI may be applicable, forexample, if the resource used for the transmission of the request isdedicated to the WTRU (e.g., the request may have been performed using aDSS, such as described herein, and/or using a dedicated signature orpreamble on the RSSC, and/or the included capability for the network todetermine the identity of the WTRU as described herein).

The DCI may schedule a RAR-like message on PDSCH that may comprise theTAC and/or TPC. For example, such DCI may comprise a downlink assignmentfor PDSCH.

The DCI and/or the PDSCH message may include the TAC and/or TPC for aWTRU. The downlink transmission on PDSCH may include an L2 message, forexample, similar to the RAR used in the random access procedure. Such L2message may comprise a TAC and/or power control information (e.g., TPC).The L2 message may comprise a CB-RNTI and/or a grant for an uplinktransmission (e.g., a contention-based grant). Such DCI may beapplicable, for example, if the resource used for the transmission ofthe request is shared for multiple WTRUs (e.g., the request may havebeen performed using a randomly selected preamble on RSSC). For example,such WTRU-specific L2 message may be utilized as response to thetransmission of an uplink synchronization request using dedicatedresources for RSSC or using DSS.

The DCI and/or the PDSCH message may comprise a DSS configuration for aWTRU. The downlink transmission on PDSCH may comprise a L2 message, forexample, similar to the RAR used in the random access procedure. Such L2message may comprise a configuration for DSS (e.g., as describedherein). The WTRU may configure the uplink synchronization proceduresuch that DSS transmissions may be used when the WTRU is synchronizedfor the WTRU-autonomous uplink synchronization procedure. When theresponse is related to the previous transmission on RSSC, the WTRU mayreceive the DSS as initial configuration. When the response may berelated to a previous transmission on DSS, such DSS configuration may beuseful. The DSS configuration may be present when the WTRU may bereallocated to a new set of resource. For example, the DSS configurationmay be valid until revoked (e.g., explicitly revoked). For example, theWTRU may invalidate and/or remove the DSS configuration when it may nolonger be synchronized to the cell, such as when the TAT expires (e.g.,this may provide control to the network to let the resources expire)and/or when a mobility event occurs. For example, the WTRU mayinvalidate and/or remove the DSS configuration when it initiates atransmission on the RSSC (e.g., such as described herein).

The DCI and/or the PDSCH message may comprise the TAC and/or TPC formultiple WTRUs. Such message may comprise multiple responses. Forexample, one or more (e.g., each) response may comprise an identifier,such as the preamble received. Such message may comprise a backoffindicator, for example, a WTRU may have transmitted a synchronizationrequest and may have received a L2 message associated with the resourceused for the transmission, which message might not comprise a responsefor the concerned WTRU. For example, the WTRU may determine that thebackoff indicator may be set and may determine an amount of time it isutilized to wait before a subsequent attempt (e.g., or retransmission)may be performed. For example, such multi-WTRU L2 message may besuitable as a response to the transmission of an uplink synchronizationrequest using shared or dedicated resources for RSSC. It may beapplicable as response to uplink synchronization request using dedicatedresources for DSS if one or more (e.g., each) WTRU may be associatedwith some index inside the response, for example, based on the resourceused.

The WTRU may receive HARQ feedback, for example in scenarios includingwhere there was data in the request. For example, the WTRU may receiveHARQ feedback associated to the transmission of such a request, forexample, perhaps if the WTRU used a transmission corresponding to a datatransmission (e.g. a transmission on a PUSCH resource), among otherscenarios. The HARQ feedback may be received according to procedure(s)applicable for such transmission (e.g. using PHICH and/or PDCCH). Inscenarios involving PDCCH, the RNTI used may be determined according toone of the procedure described herein.

For a request with data, the WTRU may try again, perhaps if it receivesHARQ NACK (for example perhaps only if it receives HARQ/NACK). The WTRUmay (e.g., autonomously) perform a further transmission (e.g. accordingto a method used for the request as described herein) perhaps forexample if the WTRU receives HARQ NACK but might not receive any otherresponse to the request, and/or might not obtain valid uplink timingsynchronization (e.g., perhaps as a result of the transmission of therequest). The further transmission may be a HARQ retransmission, perhapsfor example if the transmission for which HARQ NACK feedback wasreceived was not performed on a contention-based resource.

No response, power ramp-up and/or determining failure (e.g. RLF after xattempts) are contemplated. The WTRU may determine that no response isreceived for the request. The WTRU may perform the determination,perhaps for example after a certain time has elapsed since the lasttransmission of a request. The WTRU may determine that no HARQ feedbackis received for such last transmission. In such scenarios, among others,the WTRU may perform power ramping for the next attempt, if any, forexample. Ramping up to a maximum transmission power may be aconfigurable aspect of the WTRU. A last/previous transmission may be thelast/most previous attempt in a sequence of one or more attempts. Amaximum number of attempts may be a configurable aspect of the WTRU. TheWTRU may determine that the procedure is unsuccessful, perhaps forexample when it determines that no response has been received and/or themaximum number of attempts has been reached. In such scenarios, amongothers, the WTRU may revert to legacy procedures (e.g. random access,Radio Link Failure in CONNECTED mode, and/or cell reselection in IDLEmode).

Examples of improved access to uplink resources are contemplated.Enhanced Scheduling Request (eSR) is contemplated. The WTRU may sendmore detailed information about what it utilizes to transmit in thescheduling request, for example, instead of providing the information inthe BSR, or in an extended BSR (eBSR), for example, on CB-PUSCH. Thismay provide reduction of the overall UP latency at the expense of SRresource consumption. This may be attractive in small cell scenarios,such as where PUCCH multiplexing capacity may be higher and fewer WTRUsmay be connected. Examples described herein may be well suited for highload environments. The WTRU may transmit an enhanced scheduling request(eSR) that includes at least the following information: amount of dataavailable for transmission, and/or priority of such data; delayrequirement of data available for transmission; other QoS aspects;channel-related info (e.g., CQI, pathloss, PHR, etc.); and/or WTRUidentity.

The amount of data available for transmission, and/or priority of suchdata, for example, may include similar information as the legacy BSR.For example, the WTRU may report an amount of data at a different (e.g.,lower) granularity. For example, the priority signaled (e.g., eitherimplicitly, such as for the amount of data reported when a specificpriority is reported, or explicitly) may be for one or more (e.g., each)amount of data reported (e.g., when one amount for different prioritiesmay be reported). The priority signaled may be the priority associatedwith the data that has the highest priority in the WTRU's buffer.

The WTRU may transmit an enhanced scheduling request comprising thedelay requirement of data available for transmission. For example, theWTRU may report the amount of data that may have a delay requirementless than a threshold. For example, the WTRU may report the delayrequirement of the data that may have the most stringent delayrequirement. For example, the data considered may correspond to dataassociated to a specific priority.

The WTRU may transmit an enhanced scheduling request comprising otherQoS aspects, for example similar to those described herein.

The WTRU may transmit an enhanced scheduling request comprisingchannel-related info (CQI, pathloss, PHR, etc.). For example, the WTRUmay report information such that the network may determine the mostsuitable grant for the WTRU, or “desired” grant parameters (e.g., MCS,RB allocation, rank).

The WTRU may transmit an enhanced scheduling request comprising the WTRUidentity, for example, for shared resource for E-SR.

The WTRU may transmit an enhanced scheduling request (eSR) according tochannel selection over PUCCH or over RACH preambles (e.g., two resourcesmay be used to provide one bit of information, four resources to providetwo bits of information, etc.). The WTRU may transmit an enhancedscheduling request (eSR) according to PUCCH format 2 or format 3 and thenumber of information bits may be set by the signaling format use, forexample, the PUCCH format 2b may provide up to two bits of information.The WTRU may transmit an enhanced scheduling request (eSR) according toPUSCH (e.g., contention-based) and the number of information bits may beset by the signaling format used.

The WTRU may initiate the transmission of an enhanced scheduling request(eSR) according to UL data arrival, such as for specific bearers. TheWTRU may initiate the transmission of an enhanced scheduling request(eSR) that may be valid for a single eSR transmission, for example, ifthe WTRU has received L1/MAC signaling enabling the functionality.Signaling that may comprise indication of eSR resource to use (e.g.,that allows the network to configure >1 UE on same eSR resource withoutcollision). The WTRU may initiate the transmission of an enhancedscheduling request, for example, if a WTRU has receivedPDCCH/E-PDCCH/PDSCH within a time period. The DCI may contain indicationof eSR resource to use (e.g., to enable more accurate pre-allocationscheme).

The use of eSR may be a configuration aspect. Such SR combined withinformation (eSR) may be similar to Happy Bit(s). The transmission of asignal may correspond to the eSR (e.g., 1 bit of information), and thesignal may convey information (e.g., two bits total information). Happybits (e.g., the second bit of information and the resulting 2-bitcodepoints) may be applicable, for example, when eSR may be configuredand/or available. eSR may be applicable to one or a subset of bearers inthe WTRU's configuration. For example, the happy bits may signalinformation related to a single LCG and/or DRB or to the aggregation ofa plurality of LCGs and/or DRBs configured with eSR.

For example, the WTRU may comprise any information described herein, forexample, on a transmission on PUSCH (e.g., CB-PUSCH), such that theinformation may be transmitted as a MAC Control Element in an extendedBSR (e.g., MAC eBSR CE).

Contention-based uplink resources are contemplated. Combinations of RSSCand DSS are contemplated. Additional combinations of examples thatenable CB-PUSCH transmissions are contemplated.

For example, the WTRU may perform a transmission on CB-PUSCH. Forexample, the WTRU may perform a transmission on a different channel(e.g., PRACH, RSSC) or using a different signal (e.g., DSS, SRS, PUCCH)for resolving contention. If the WTRU may have a valid DSSconfiguration, and/or if such resource may be dedicated to the WTRU, theWTRU may access the CB-PUSCH channel and transmit data in the uplinkwhile performing a DSS transmission. The network may determine the WTRUsthat may have performed the uplink transmission or determine whether ornot a collision may have occurred on the CB-PUSCH.

The WTRU may use a WTRU-specific DM-RS resource and/or pattern onCB-PUSCH. The WTRU may perform a transmission on. CB-PUSCH using (e.g.,second) transmission methods (e.g. non-orthogonal transmission and/orusing a waveform that does not have tight synchronization requirement).Such a transmission may be performed using a configured grant and/orresource, for example, in which the WTRU may perform an uplinktransmission perhaps if there is data to transmit (e.g., perhaps only ifthere is data to transmit), and/or if the WTRU determines that it mayinitiate the uplink synchronization request procedure as describedherein.

Pre-allocation is contemplated. The WTRU may determine the grantparameters, for example, without receiving a dynamic grant. This mayallow the WTRU to start PHY processing, for example, as soon as the datamay be received instead of waiting for a DCI. The WTRU may pick frommore than one set of parameters and an indication may be provided toease blind decoding. To enable contention, the WTRU may use a smalldedicated resource (e.g., PUCCH, SR) to indicate that it may betransmitting or going to transmit, and on which resource.

The PDCCH order for CFRA may be an opportunity for the WTRU to performSR+TA using a resource allocated, for example, using a dedicated grant(e.g., instead of a contention-based grant). Dynamic scheduling of PRACHresources for RA-SR may be used, for example, dynamic scheduling ofPRACH resources for RA-SR may be performed for WTRUs with dedicatedpreambles but not for WTRUs with non-dedicated preambles.

The WTRU may perform autonomous selection and/or determination for atleast one of the following parameters associated to a grant: MCS; RBallocation; rank; bundling with number of repetitions (e.g., to addresspower limitations/cell edge); max HARQ (e.g., to address powerlimitations/cell edge); power (e.g., may use same formula with specificoffset to compensate for the lack of power accuracy when the WTRU mightnot have transmitted for a long time); etc. The WTRU may determine suchparameters according to at least one of the following: the amount ofbuffered data, for example, from a high-priority logical channel; thechannel-related info (e.g., CQI, pathloss, PHR, etc.), such as somethingthat depends on link quality.

For parameters for which the WTRU has autonomously determined a value,the WTRU may signal together with the transmission such that the WTRUmay comprise the index to grant/resource parameters and/or the WTRUidentity. For parameters for which the WTRU has autonomously determineda value, the WTRU may signal together with the transmission in PUSCH,for example using puncturing (e.g., similar to RI or A/N, possibly inplace of RI or A/N). For parameters for which the WTRU has autonomouslydetermined a value, the WTRU may signal together with the transmissionin (e.g., dedicated) PUCCH resource and may or might not be in samesubframc.

The WTRU may use such examples when at least one of the followingoccurs: UL data arrival; if pre-defined grant resource may be availablebefore N subframes (e.g., or if it allows for reduced latencyconsidering timing of regular SR resource); if the WTRU has receivedL1/MAC signaling enabling the functionality (e.g., signaling maycomprise a set of possible resources and grant parameters and resourcefor associated signaling); and/or if the WTRU has receivedPDCCH/E-PDCCH/PDSCH within a time period.

Combinations of RSSC, DSS, L3 Connection Reactivation, extended Paging,and eSR are described herein.

FIG. 6 shows examples of signaling that may be used. For example,different combinations of RSSC, DSS, L3 Connection Reactivation,extended paging, and/or eSR may be used.

The techniques described for the use of RSSC, DSS, L3 ConnectionReactivation, extended paging, and/or eSR may be applicable to any modeof operation, any trigger to perform autonomous uplink synchronization,and/or any transitions from an unsynchronized to synchronized state. TheRSSC transmission, use of dedicated synchronization signals, Layer 3/RRCreactivation, and/or techniques for Downlink or Uplink UP data arrivalbe performed individually or in any combination.

An example, at 6002 in FIG. 6, a request for initial synchronization maybe transmitted. For example, the WTRU may determine that it does nothave a valid/up-to-date/accurate uplink synchronization. The WTRU maydetermine that resources for autonomously maintaining uplinksynchronization are available in the cell. If the WTRU has dataavailable for transmission and/or the WTRU is configured with a secondtransmission method (e.g., the second transmission method may beperformed even when the WTRU does not have uplink synchronization), suchas a second transmission method on a CB-PUSCH channel, e.g., the WTRUmay perform a transmission in accordance with the second transmissionmethod. For example, a transmission on the CB-PUSCH or other resourcesassociated with the second transmission method may be self-contained(e.g., the network may be able determine the identity of the WTRU fromthe successful reception of the transmission). If the WTRU determinesthat it should obtain uplink synchronization prior to uplinktransmission (e.g., the WTRU determines it is configured to autonomouslymaintain valid uplink timing alignment), the WTRU may initiate theuplink synchronization procedure by transmitting a preamble on the RSSC.

The WTRU may perform various action if an attempt to obtain uplinksynchronization on the RSSC is unsuccessful. For example, in the absenceof a response to the RSSC transmission (e.g., the absence of a responsewithin a specific time following the transmission of a preamble or otherevent related to the RSSC transmission), the WTRU may apply some backofftime and/or may perform a retransmission for example after the backofftime has elapsed. For example, the re-transmission on the RSSC may beperformed with increased transmission power. In the absence of aresponse (e.g., absence of a response within a certain number oftransmissions or retransmissions), the WTRU may determine that theprocedure is unsuccessful and attempt to send a scheduling request usinga random access channel (e.g., revert to the legacy RA-SR procedure)

Also shown at 6002 in FIG. 6 is a response to the RSSC request and/orthe transmission using the second transmission method (e.g., thetransmission method where the WTRU transmits without uplinksynchronization). The response may include initial synchronizationinformation. For example, the WTRU may receive a Timing Advance Command(TAC). The WTRU may receive a power control command (TPC), e.g., todetermine the initial transmission power for subsequent transmissions.Initial transmission power may remain valid, e.g., as long as thepathloss estimate criterion (e.g., pathloss estimate criterion asdescribed for determining if DL timing has changed) is not met (e.g., aslong as the pathloss estimate change does not change by more than aspecific threshold subsequent to the reception of such TPC).

Once the WTRU has obtained an initial uplink timingalignment/synchronization, the WTRU may maintain valid uplink timingalignment according to any example described herein (e.g., by RSSC, DSS,random access, etc.).

Synchronization may be maintained by the WTRU while operating in anymode or based on any synchronization trigger by using the RSSC. 6004 inFIG. 6 illustrates the WTRU maintaining synchronization. For example,the WTRU may determine that it currently has valid uplinksynchronization. The WTRU may determine that it is configured toautonomously maintain the valid uplink timing alignment. The WTRU maydetermine that resources for autonomously maintaining uplinksynchronization may be available in the cell. Perhaps for example, ifthe WTRU has data available for transmission and/or the WTRU isconfigured with a second/different transmission method for transmissionon a CB-PUSCH channel, e.g., the WTRU may perform such transmission.Perhaps for example if the WTRU determines that is may have lost uplinksynchronization (e.g. the WTRU determines that the downlink timingreference has changed by more than a configured threshold since it lastreceived a TAC), the WTRU may initiate the uplink synchronizationprocedure by transmitting a preamble on the RSSC.

The WTRU may determine that the attempt to maintain uplinksynchronization using the RSSC was unsuccessful. For example, in theabsence of a response within a time (e.g., a specific time following thetransmission of a preamble), the WTRU may apply some backoff time and/orperform a retransmission, e.g., with increased transmission power. Inthe absence of a response within a certain number of retransmissions,the WTRU may determine that the procedure is unsuccessful and/or revertto, e.g., the legacy RA-SR procedure when triggered using legacymethods.

As shown at 6004 in FIG. 6, the WTRU may receive a response, formaintaining the (e.g., initial) synchronization. The WTRU may receive aTiming Advance Command (TAC). The WTRU may receive a power controlcommand (TPC) (e.g., to determine the initial transmission power forsubsequent transmissions). Initial transmission power may remain valid,for example, as long as the pathloss estimate criterion or othercriteria for determining a relative change in DL timing is not present(e.g., as long as the pathloss estimate change does not change by morethan a specific threshold subsequent to the reception of such TPC).

The WTRU may subsequently maintain valid uplink timing alignment, e.g.,according to an example described herein (e.g., by DSS).

Synchronization may be maintained by the WTRU while operating in anymode or based on any synchronization trigger by using the DSS. Forexample, as shown at 6004 of FIG. 6, the WTRU may determine that it hasvalid uplink synchronization. The WTRU may determine that it isconfigured to autonomously maintain valid uplink timing alignment usinga dedicated transmission (e.g., via DSS), for example using an SRS-likesignal on a dedicated resource in time-frequency domain. The WTRU maydetermine that it has a valid transmission power setting for the uplinktransmission. If The WTRU determines it does not have validsynchronization, the WTRU may revert to a transmission on RSSC, asdescribed herein. If the WTRU has data available for transmission,and/or the WTRU is configured with a second transmission method fortransmission on a CB-PUSCH channel, e.g., the WTRU may perform suchtransmission. If the WTRU determines that its synchronization state mayhave changed (e.g., the WTRU determines that the downlink timingreference has changed, such as changing by more than a configuredthreshold since it last received a TAC), the WTRU may initiate theuplink synchronization procedure by transmitting a signal on thededicated resource.

The WTRU may determine that the attempt to maintain uplinksynchronization using the DSS was unsuccessful. For example, the WTRUmight not receive a response within a specific time following thetransmission on a dedicated resource. If the WTRU does not receive aresponse within a specific time following the transmission on adedicated resource, the WTRU may perform a retransmission at asubsequent occasion. The WTRU may determine that the attempt to maintainuplink synchronization using the DSS is unsuccessful (e.g., in theabsence of a response within a certain number of re-transmissions. Ifthe WTRU determines that the attempt to maintain uplink synchronizationusing the DSS is unsuccessful, the WTRU may revert to a transmission(e.g., on RSSC) as described herein, or to the legacy RA-SR procedurewhen triggered using legacy methods.

As shown in 6004 in FIG. 6 the WTRU may receive a response, for initialsynchronization. The WTRU may receive a Timing Advance Command (TAC).For example, the WTRU may receive a power control command (TPC) todetermine the initial transmission power for subsequent transmissions.The initial transmission power may remain valid e.g., as long as thepathloss estimate criterion is not met (e.g., as long as the pathlossestimate change does not change by more than a threshold subsequent tothe reception of such TPC).

The WTRU may maintain valid uplink timing alignment, e.g., according toan example described herein (e.g., by RSSC).

The WTRU may be configured to handle Downlink Data Arrival whileoperating in IDLE mode. FIG. 7 shows an example of signalling techniquesdescribed herein for a WTRU in IDLE mode in case of downlink dataarrival (e.g., with L3 Connection Reactivation).

For example, to process downlink data arrival while operating in IDLEmode the WTRU may or might not be synchronized. If the WTRU is in RRCIDLE mode and/or it does not have valid uplink timing alignment (e.g.,the WTRU is not synchronized), the WTRU may autonomously initiate thetransition from unsynchronized to synchronized (e.g., as describedherein, and/or corresponding to 6002 in FIG. 6/FIG. 7).

The WTRU may initiate an autonomous synchronization procedure asdescribed herein which may allow it to process data faster than legacybehaviour. For example, if the WTRU performs autonomous UL timingalignment (e.g., via the RSSC), and if the WTRU received extended pagingthat schedules a transmission (e.g., downlink and/or uplink) the WTRUmay be able to process the transmission quickly. For example, the WTRUmay determine which synchronization procedure (e.g., autonomous usingRSSC/DSS or legacy using RACH) the WTRU may be able to complete thefastest and/or select the faster procedure for performing thesynchronization. For example, if the initial page includes schedulinginformation and the WTRU determines that the autonomous timingsynchronization procedure can be completed in time to perform thetransmission in accordance with the received scheduling information,then the WTRU may initiate the autonomous timing synchronizationprocedure. If the WTRU determines that it cannot complete the autonomoustiming procedure and/or such a procedure is unsuccessful, the WTRU mayperform legacy procedure(s) for the applicable mode of operation (e.g.such as RRC IDLE mode procedures), such as the legacy RRC ConnectionEstablishment Request procedure (e.g., such as initiating the randomaccess procedure on PRACH resources of the cell).

The WTRU may receive control signalling that indicates a PDSCHtransmission that includes RRC Reactivation and/or configurationinformation. For example, the WTRU may receive control signalling in thedownlink that may indicate a downlink transmission on PDSCH for theWTRU. Such control signalling may, e.g., be extended paging signalling,as described herein. The WTRU may receive the PDSCH transmission. ThePDSCH transmission may, e.g., include user plane data for the WTRU (e.g.for short data transfer) and/or control plane signalling (e.g., L3signalling) that configures a connection. L3 signalling may include aRRC Connection Reconfiguration message (e.g., that reactivates and/orre-configures a RRC Connection, for example such as a reactivation of apreviously used RRC Connection and/or RRC context).

WTRU may transmit a response to indicate completion of RRC Connectionconfiguration. The WTRU may, e.g., once it has successfully reactivatedand/or re-configured the RRC Connection, initiate the transmission of aresponse, such as a RRC Connection Reconfiguration Complete message.

For example, the WTRU may be configured to set a priority amongsignalling procedures such that WTRU first checks for dedicated grants(e.g., paging or PDCCH), then processes a CB-PUSCH if available, andthen reverts to use of the RACH. In other examples, such procedures maybe performed contemporaneously or in a different order.

For example, the WTRU may determine whether or not a grant for adedicated transmission on the PUSCH was received, e.g., in the extendedpaging signalling. If a dedicated grant is received, the WTRU maytransmit a response using the associated resources. For example, theWTRU may decode DCIs on PDCCH for a certain period of time using theC-RNTI associated with the (e.g., possibly re-activated) RRC Connectionas configured and/or established from the reception of the L3signalling. For example, the WTRU may decode DCIs on PDCCH for a certainperiod of time using the C-RNTI associated with the RRC Connection if agrant for a dedicated transmission on PUSCH was not received. The WTRUmay, e.g., if the WTRU successfully decodes such grant, transmit theresponse using the associated resources. If the WTRU does notsuccessfully receive a grant (e.g., within a possibly configuredperiod), the WTRU may initiate the random access procedure on PRACHresources of the cell. Rather than or in addition to initiating randomaccess, the WTRU may determine whether there is a CB-PUSCH resourceavailable to the WTRU (e.g., possibly within a certain amount of time).

The WTRU may, e.g., if the CB-PUSCH resource is available, transmit theresponse using the associated resources. Perhaps for example if the WTRUdoes not identify a suitable resource for a PUSCH transmission for theL3 response, and/or if the WTRU determines that the transmission usingthe determined resource is unsuccessful, the WTRU may initiate therandom access procedure on PRACH resources of the cell for thereactivated and/or established RRC Connection. Subsequently or inparallel, the WTRU may perform legacy procedure(s) for the applicablemode of operation (e.g., such as RRC IDLE mode procedures) such as thelegacy RRC Connection Establishment Request procedure (e.g., which mayalso involve initiating the random access procedure on PRACH resourcesof the cell).

An example of the L3 signalling is shown in at 6006 in FIG. 6/FIG. 7.This may apply to the RRC-Inactive mode, if such a mode is supported bythe WTRU.

In one or more techniques, 6002 may be performed as part of 6006,perhaps instead of the WTRU's transmission of the L3 ReactivationComplete message and/or the first user plane data, perhaps for exampleif a second type of transmission may be used for the RSSC such that datamay be included on the transmission for the RSSC, for example.

The WTRU may be configured to handle Uplink Data Arrival while operatingin IDLE mode. FIG. 8 shows an example of signalling techniques describedherein for a WTRU in IDLE mode in case of uplink data arrival (e.g. withL3 Connection Reactivation).

The WTRU may autonomously initiate the transition from unsynchronized tosynchronized. For example, the WTRU may autonomously initiate thetransition from unsynchronized to synchronized as described hereinand/or shown in 6002 of FIG. 6/FIG. 8. The WTRU may autonomouslyinitiate the transition from unsynchronized to synchronized, perhaps forexample if the WTRU is in RRC IDLE mode and/or the WTRU does not havevalid uplink timing alignment (e.g., the WTRU is not synchronized).

For example, the WTRU may initiate synchronization, perhaps for exampleif it can be faster than legacy behaviour (e.g., if the WTRU is in RRCIDLE mode and/or the WTRU does have valid uplink timing alignment),among other scenarios.

The WTRU may initiate synchronization if the WTRU determines thatCB-PUSCH resources are available (e.g., if the WTRU determines that theWTRU may complete the synchronization procedure on time for a requireduplink transmission, e.g., on (CB-) PUSCH). The WTRU may perform legacyprocedure(s) for the applicable mode of operation (e.g., such as RRCIDLE mode procedures) such as the legacy RRC Connection EstablishmentRequest procedure. For example, the WTRU may perform legacy procedure(s)for the applicable mode of operation if the WTRU might not complete thesynchronization procedure on time for a required uplink transmission.

The WTRU may initiate transmission of L3 control signalling. The WTRUmay initiate the transmission of data. Such data may include user planedata (e.g., a small data transfer). Such data may be control planesignalling (e.g., L3 signalling) that may request the establishmentand/or the reactivation of a connection. Such L3 signalling, may includea RRC Connection Establishment (or Re-establishment) Request message,for example, that requests a re-configuration and/or a reactivation of aRRC Connection (e.g. such as a reactivation of a previously used RRCConnection and/or RRC context).

A check for CB-PUSCH, and/or RACH, is contemplated. At 6008, the WTRUmay determine whether there is a CB-PUSCH resource available to the WTRU(e.g., possibly within a certain amount of time). This determination ofa CB-PUSCH resource may be performed first. Perhaps for example, if sucha resource is available, the WTRU may transmit the data using theassociated resources. Perhaps for example if the WTRU does not determinea suitable resource for a PUSCH transmission for the data, and/or if theWTRU determines that the transmission using the determined resource isunsuccessful, the WTRU may perform legacy procedure(s) for theapplicable mode of operation (e.g., such as RRC IDLE mode procedures)such as the legacy RRC Connection Establishment Request procedure, e.g.,which may involve initiating the random access procedure on PRACHresources of the cell.

The WTRU may receive a L3 response. The WTRU may receive controlsignalling in the downlink that indicates (e.g., a downlink transmissionon PDSCH for the WTRU). The WTRU may decode DCIs on PDCCH for a certainperiod of time using the C-RNTI associated to the RRC Connectionassociated to the re-activation request (if applicable). If the WTRUsuccessfully decodes such downlink assignment, the WTRU may receive atransmission on the PDSCH. The PDSCH transmission may include, e.g.,user plane data for the WTRU (e.g. for short data transfer) and/orcontrol plane signalling (e.g. L3 signalling) that configures aconnection. Such L3 signalling may, e.g., include a RRC ConnectionReconfiguration message that, e.g., reactivates and/or re-configures aRRC Connection, such as a reactivation of a previously used RRCConnection and/or RRC context, e.g., using the connection associated tothe request previously sent by the WTRU.

A WTRU may transmit a response, e.g., to indicate completion of RRCConnection configuration

The WTRU may (for example perhaps once it has successfully received L3signalling and/or reactivated and/or re-configured the RRC Connection)initiate the transmission of a response, such as a RRC ConnectionReconfiguration Complete message.

The WTRU may check for dedicated grant (PDCCH), and/or CB-PUSCH, and/orRACH.

The WTRU may determine whether a grant for a dedicated transmission onPUSCH is available, e.g. by decoding PDCCH possibly during a certainamount of time for a DCI that includes a grant for an uplinktransmission using the C-RNTI associated to the (possibly re-activated)RRC Connection as configured and/or established from the reception ofthe L3 signalling. For example, the WTRU may perform this determinationfirst, among other scenarios. The WTRU may transmit the response usingthe associated resources, e.g., if the WTRU determines that a grant fora dedicated transmission on PUSCH is available. The WTRU may, e.g., ifthe WTRU determines that a grant for a dedicated transmission on PUSCHis not available, initiate the random access procedure on PRACHresources of the cell. The WTRU may determine whether there is aCB-PUSCH resource available to the WTRU (e.g., possibly within a certainamount of time). The WTRU may, e.g., if such resource is available,transmit the response using the associated resources. The WTRU may,e.g., if the WTRU does not determine a suitable resource for a PUSCHtransmission for the L3 response, perform legacy procedure(s) for theapplicable mode of operation (e.g. such as RRC IDLE mode procedures)such as the legacy RRC Connection Establishment Request procedure, e.g.which may also involve initiating the random access procedure on PRACHresources of the cell.

The WTRU might not receive any L3 response. The WTRU may, perhaps forexample if the WTRU might not successfully receive a transmission onPDSCH, perform legacy procedure(s) for the applicable mode of operation(e.g., such as RRC IDLE mode procedures), such as the legacy RRCConnection Establishment Request procedure, which may involve initiatingthe random access procedure on PRACH resources of the cell.

Such signalling is shown at 6006 in FIG. 6/FIG. 8. This may apply to theRRC-Inactive mode (e.g., if such a mode is supported by the WTRU).

For example, 6002 may be used for the WTRU's transmission of the L3Reactivation Request message and/or the first user plane data, perhapsfor example if a second type of transmission may be used for the RSSCsuch that data may be included on the transmission for the RSSC.

Connected mode and/or downlink data arrival is contemplated. FIG. 9shows an example of signalling techniques of the methods describedherein for a WTRU in CONNECTED mode in case of downlink data arrival.

Perhaps for example if the WTRU is in RCC CONNECTED mode and/or does nothave valid uplink timing alignment (e.g., the WTRU is not synchronized),the WTRU may autonomously initiate the transition from unsynchronized tosynchronized (e.g., as described in herein and corresponding to 6002 inFIG. 6/FIG. 9.

The WTRU may receive DCI on PDCCH for reception of PDSCH. The WTRU mayreceive control signalling on PDCCH that may indicate a downlinktransmission on PDSCH for the WTRU. In such scenarios, among others, theWTRU may transmit HARQ ACK/NACK signalling for the receivedtransmission, perhaps for example when it (e.g., autonomously) maintainsuplink timing alignment.

The handling of error cases, such as a mismatch between network (NW) andthe WTRU is contemplated. Perhaps for example if the WTRU might not havea valid uplink timing alignment, the WTRU may initiate the random accessprocedure on PRACH resources of the cell, for example such that it mayobtain uplink timing alignment. This may enable the NW to detect theerror case, for example where the NW may have assumed (e.g. incorrectly)that the WTRU was successful in autonomously maintaining valid uplinktiming alignment, and/or the NW may restart the transmission of thedownlink data. Example signalling is shown at 6010 in FIG. 6/FIG. 9.This may apply to the RRC-Inactive mode, if such a mode is supported bythe WTRU.

Connected mode and/or Uplink Data Arrival, is contemplated. FIG. 10shows an example of signalling techniques described herein for a WTRU inCONNECTED mode in case of uplink data arrival.

The WTRU may or might not be synchronized. Perhaps for example, if theWTRU is in RCC CONNECTED mode and/or does not have valid uplink timingalignment (e.g., the WTRU is not synchronized), the WTRU mayautonomously initiate the transition from unsynchronized tosynchronized, e.g., as described herein and/or corresponding to 6002 inFIG. 6/FIG. 10.

The WTRU may determine that it has new (e.g., fresh) data available fortransmission. For example, the new data available for transmission mayinclude data associated with a (e.g., specific by configuration) DataRadio Bearer (DRB). The determination of whether the WTRU has new dataavailable for transmission might not be applicable to higher prioritytransmissions (e.g., to data associated with a Signalling Radio Bearer(SRB)).

The WTRU may check for CB-PUSCH, and/or RACH. The WTRU may for exampledetermine whether there is a CB-PUSCH resource available to the WTRU(e.g., within a certain amount of time). For example, the WTRU may makethis determination first. The WTRU may (e.g., if the CB-PUSCH resourceis available) transmit the data using the associated resources. The WTRUmay (e.g. if the WTRU does not determine a suitable resource for a PUSCHtransmission for the data and/or if the WTRU determines that thetransmission using the determined resource is unsuccessful) performlegacy procedure(s) for the applicable mode of operation. The WTRU mayuse a Scheduling Request according to D-SR on PUCCH (e.g., ifconfigured) and/or RA-SR on PRACH.

The WTRU may perform methods described herein, including eSR. Suchsignalling is shown at 6012 in FIG. 6/FIG. 10. The above may apply tothe RRC-Inactive mode (e.g., if such a mode is supported by the WTRU).

For example, 6002 may be used for the WTRU's transmission of the firstuser plane data, perhaps for example if a second type of transmissionmay be used for the RSSC such that data may be included on thetransmission for the RSSC.

The processes and instrumentalities described herein may apply in anycombination, may apply to other wireless technologies, and for otherservices. Although features and elements are described herein in examplecombinations, one of ordinary skill in the art will appreciate that oneor more, or each, feature or element can be used alone or in anycombination with any of the other features and elements. The processesdescribed above may be implemented in a computer program, software,and/or firmware incorporated in a computer-readable medium for executionby a computer and/or processor. Examples of computer-readable mediainclude, but are not limited to, electronic signals (transmitted overwired and/or wireless connections) and/or computer-readable storagemedia. Examples of computer-readable storage media include, but are notlimited to, a read only memory (ROM), a random access memory (RAM), aregister, cache memory, semiconductor memory devices, magnetic mediasuch as, but not limited to, internal hard disks and removable disks,magneto-optical media, and/or optical media such as CD-ROM disks, and/ordigital versatile disks (DVDs). A processor in association with softwaremay be used to implement a radio frequency transceiver for use in a WTRU(UE), terminal, base station, RNC, and/or any host computer.

What is claimed is:
 1. A method for communicating data performed by awireless transmit/receive unit (WTRU), the method comprising:determining, by the WTRU, that at least one of: control plane data oruser plane data is available for transmission to a network; determining,by the WTRU, that the WTRU is in at least one of: a radio resourcecontrol (RRC) IDLE mode or a RRC CONNECTED mode; determining, by theWTRU, that the WTRU is in an unsynchronized state relative to thenetwork; determining a spectrum operational mode (SOM) for atransmission, the SOM indicating at least one of: a subcarrier spacing,a transmission time interval (TTI) length, or a waveform for thetransmission; sending the transmission from the WTRU in theunsynchronized state, via a physical uplink channel to the network, thetransmission including: the at least one of the control plane data orthe user plane data; and an uplink timing synchronization request; andreceiving, by the WTRU, at least one of a timing advance command (TAC)or a transmit power command (TPC) from the network in response to thetransmission.
 2. The method of claim 1, further comprising: receiving,by the WTRU, one or more parameters from the network for accessing acontention-based Physical Uplink Shared Channel (CB-PUSCH) in responseto the transmission.
 3. The method of claim 1, wherein one or moreoccasions of the physical uplink channel correspond to the SOM.
 4. Themethod of claim 1, wherein one or more resources of the physical uplinkchannel correspond to the SOM.
 5. The method of claim 1, furthercomprising: determining, autonomously by the WTRU, to send thetransmission.
 6. The method of claim 1, wherein the transmission doesnot indicate an identity of the WTRU.
 7. The method of claim 1, whereinthe physical uplink channel is a shared channel.
 8. The method of claim1, wherein the physical uplink channel is a Random SharedSynchronization Channel (RSSC).
 9. The method of claim 1, wherein thetransmission via the physical uplink channel reduces latency relative toat least one of: a random access channel (RACH) procedure, a radioresource control (RRC) connection establishment procedure, or a datapacket scheduling.
 10. The method of claim 1, wherein the control planedata includes as least one of an RRC Establishment Request, an RRCRe-establishment Request, or an RRC Connection Reactivation Request. 11.The method of claim 1, wherein the transmission is conducted using afiltered waveform that is characterized by relatively high spectralcontainment.
 12. A wireless transmit/receive unit (WTRU), comprising: aprocessor, the processor configured at least to: determine that at leastone of: control plane data or user plane data is available fortransmission to a network; determine that the WTRU is in at least oneof: a radio resource control (RRC) IDLE mode or a RRC CONNECTED mode;determine that the WTRU is in an unsynchronized state relative to thenetwork; and determine a spectrum operational mode (SOM) for atransmission, the SOM indicating at least one of: a subcarrier spacing,a transmission time interval (TTI) length, or a waveform for thetransmission; a transmitter, the transmitter configured at least to:send the transmission in the unsynchronized state, via a physical uplinkchannel to the network, the transmission including: the at least one ofthe control plane data or the user plane data; and an uplink timingsynchronization request; and a receiver, the receiver configured atleast to: receive at least one of a timing advance command (TAC) or atransmit power command (TPC) from the network in response to thetransmission.
 13. The WTRU of claim 12, wherein the processor is furtherconfigured to: receive one or more parameters from the network foraccessing a contention-based Physical Uplink Shared Channel (CB-PUSCH)in response to the transmission.
 14. The WTRU of claim 12, wherein theprocessor is further configured to: autonomously determine to send thetransmission.
 15. The WTRU of claim 12, wherein the transmission via thephysical uplink channel reduces latency relative to at least one of: arandom access channel (RACH) procedure, a radio resource control (RRC)connection establishment procedure, or a data packet scheduling.
 16. TheWTRU of claim 12, wherein the transmitter is further configured suchthat the transmission is conducted using a filtered waveform that ischaracterized by relatively high spectral containment.